On Sun, 22 Dec 2024 14:05:51 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

>Cursitor Doom <cd@notformail.com> wrote:
>
>> On Sun, 22 Dec 2024 12:37:37 +0000, liz@poppyrecords.invalid.invalid
>> (Liz Tuddenham) wrote:
>>
>> >Jeroen Belleman <jeroen@nospam.please> wrote:
>> >
>> >> On 12/21/24 14:57, Cursitor Doom wrote:
>> >> > On Sat, 21 Dec 2024 08:57:51 +0000, liz@poppyrecords.invalid.invalid
>> >> > (Liz Tuddenham) wrote:
>> >> >
>> >> >> Cursitor Doom <cd@notformail.com> wrote:
>> >> >>
>> >> >>> On Sat, 21 Dec 2024 00:05:08 +0100, Jeroen Belleman
>> >> >>> <jeroen@nospam.please> wrote:
>> >> >>>
>> >> >>>> On 12/20/24 22:16, Cursitor Doom wrote:
>> >> >>>>> On Fri, 20 Dec 2024 19:32:14 +0000, liz@poppyrecords.invalid.invalid
>> >> >>>>> (Liz Tuddenham) wrote:
>> >> >>>>>
>> >> >>>>>> Cursitor Doom <cd@notformail.com> wrote:
>> >> >>>>>>
>> >> >>>>>>> Do we have any French speakers on the Panel? I have a radio
>> >> >>>>>>> that's badly in need of realignment and the only instructions I
>> >> >>>>>>> can find are a set in French. I can't use Google translate
>> >> >>>>>>> because they've used too many abbreviations in the text and
>> >> >>>>>>> they won't parse any sense.
>> >> >>>>>>
>> >> >>>>>> I'm not a particularly fluent French speaker, but I could
>> >> >>>>>> probably sort out some technical instructions in French If you
>> >> >>>>>> want to send them to me, I'll have a go (you should be able to
>> >> >>>>>> work out my e-mail address).
>> >> >>>>>
>> >> >>>>> Many thanks indeed for your kind offer. I suspect it will
>> >> >>>>> probably require a native French speaker to decypher, but who
>> >> >>>>> knows? :-)
>> >> >>>>
>> >> >>>> I'm not a native French speaker, but I may be able to help anyway.
>> >> >>>> Fire away.
>> >> >>>
>> >> >>> Well that's interesing as I had did think you might respond given some
>> >> >>> of the background you've revealed here in the past. I don't have the
>> >> >>> relevant page here right now, but will make it available tomorrow. It
>> >> >>> is only the one page and only one column of that, so nothing too
>> >> >>> onerous. I did show it to a genuine French chum of mine a few weeks
>> >> >>> ago, but he was stumped by the technical side of it and couldn't
>> >> >>> assist much, unfortunately. So it appears it needs someone who can
>> >> >>> speak French fluently *and* understands the process of radio
>> >> >>> alignment. I kind of guessed that might be you....
>> >> >>
>> >> >>
>> >> >> Many years ago Practical Wireless published an article about the French
>> >> >> 819-line high-definition television service which had been translated
>> >> >>from French by someone who knew nothing about television or radio
>> >> >> terminologyy. It was hilarious nonsense but I eventually managed to
>> >> >> translate it back into French so that I could understand it.
>> >> >>
>> >> >> If you post your text here, we can all have a go at it.
>> >> >
>> >> > Sorry for the delay; took a bit of tracking down but I have it now:
>> >> >
>> >> > https://disk.yandex.com/i/3SiZ6rN_k-fP4w
>> >> >
>> >> > It's only page 1 that needs the translation - and of that, in
>> >> > particular the abbreviated bits. I haven't read French since I was in
>> >> > school about a hundred years ago, so it's all Dutch to me. :-)
>> >>
>> >>
>> >> This was translated from German into French by someone who also
>> >> did not know clearly what it all meant. Not everything makes
>> >> perfect sense.
>> >>
>> >> Also, while it doesn't say so, many of the adjustments interact,
>> >> so you may have to go back and forth a few times. Anyway, here
>> >> goes.
>> >>
>> >> Jeroen Belleman
>> >>
>> >>
>> >> ===============================================================
>> >>
>> >> -- DC current adjustments (for 9V supply)
>> >> - Adjustment of the push-pull audio stage:
>> >> Cut the solder bridge marked -x- in the collector trace of the
>> >> AC188 T11 and insert a current meter. Adjust R410 for 6.5mA.
>> >> Restore the bridge.
>> >> - Adjustment of the IF amplifier:
>> >> Set R515 to obtain 1.35V across T4's emitter resistor R518.
>> >>
>> >> -- Adjustment of the FM-IF stages. The radio should be set to "FM".
>> >> Connect a wobbulator centered on 10.7MHz at MP5 and the diode
>> >> detector shown at ZF VII (I think...) MP6. Detune ZF VIII (a).
>> >> Then tune ZFVII (b) for a symmetrical maximum response.
>> >> - Inject signal at MP3 and tune ZF VI (c) and ZF V (d) for
>> >> symmetrical maximum response.
>> >> - Inject signal on MP2 and adjust ZF IV (e) and ZF III (f) for
>> >> symmetrical maximum response.
>> >> - Inject a weakly coupled signal at the mixer (MP1?) and adjust
>> >> ZF II (g) and ZF I (h) for symmetrical maximum response.
>> >> - Discriminator: Inject signal at MP5, with a level low
>> >> enough that no limiting occurs in the IF strip. Observe the
>> >> signal at MP11 (audio amplifier input) with load impedance 50k.
>> >> Adjust ZF VIII (a) for symmetrical response.
>> >>
>> >> -- Adjustment of the AM IF (460kHz) stages. The radio should be
>> >> set to "PO" (AM, 560-1450kHz). Connect a measurement instrument
>> >> at MP4 (Weakly coupled).
>> >> - Inject a wobbulator signal at MP3 and adjust ZF XIII and ZF XII
>> >> for symmetrical maximum response.
>> >> - Inject signal at MP8 and adjust ZF XI for symmetrical maximum
>> >> response.
>> >> - Inject signal at MP7 and adjust ZF X and ZF IX for symmetrical
>> >> maximum response.
>> >>
>> >> -- Adjustment of local oscillator and AM input. For short and
>> >> medium wave, couple signal into the ferrite rod antenna using
>> >> the frame. For short wave, remove the rod antenna and couple
>> >> signal at the antenna connection through 15pF.
>> >> Tune to 560kHz and adjust (1) and (3) for maximum response.
>> >> Mixer sensitivity 13uV and oscillator output 60-90mV.
>> >> Tune to 1450 kHz and adjust (2) and (4) for maximum response.
>> >> - Set the radio to GO (Long wave, 160-240kHz).
>> >> Tune to 160kHz and adjust (5) and (6) for maximum response.
>> >> Mixer sensitivity 13uV and oscillator output 65-95mV.
>> >> - Set the radio to OC (Short wave, 6.5-15MHz)
>> >> Tune to 6.5MHz and adjust (8) and (10) for maximum response.
>> >> Tune to 15MHz and adjust (9) and (11) for maximum response.
>> >> Mixer sensitivity 5uV and oscillator output 35-90mV.
>> >>
>> >> -- Adjustment of the FM LO. Signal from an RF generator with
>> >> 60 Ohm output impedance injected directly at the mixer (MP1?)
>> >> with a loaded signal level <2mV. Set the radio to FM.
>> >> - Tune to 88MHz and adjust (A) and (C) for maximum response.
>> >> - Tune to 106MHz and adjust (B) and (D) for maximum response,
>> >> Noise level is about 5 times kT0. Oscillator output voltage
>> >> 75-85mV (at T2's emitter).
>> >
>> >It is interesting to compare the different approaches Jeroen and I have
>> >taken. Although we began with exactly the same source material, we have
>> >produced two markedly different ways of saying the same thing.
>>
>> Well, the important thing is that you agree on the key points.
>> Now it just so happens I have a vintage wobbulator (made by Knight
>> IIRC) which would be ideal for this job. It hasn't been used for about
>> 20 years so it'll probably explode at switch-on, but that's nothing
>> unusual around here as my neighbours will attest.
>
>Just to reinforce the point that Jeroen made, the adjustments interact,
>so you will have to hop back and forth until the error becomes
>negligible. As far as I know. nobody has ever found a way around this
>and it takes up a lot of time at the end of a production line.
>
>A piece of equipment, which was a great help when I had that unenviable
>job, was a signal generator with push buttons to rapidly and reliably
>switch between the end-of-band spot frequencies. I still had to wind
>the dial drive from one end to the other each time - the reduction ratio
>was 110:1. (See <https://eddystoneusergroup.org.uk/Data Sheets/EC10 Oct
>1967.pdf>.)

On Sun, 22 Dec 2024 15:52:08 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 12/22/24 14:27, Cursitor Doom wrote:
>> On Sun, 22 Dec 2024 12:37:37 +0000, liz@poppyrecords.invalid.invalid
>> (Liz Tuddenham) wrote:
>>
>>> Jeroen Belleman <jeroen@nospam.please> wrote:
>>>
>>>> On 12/21/24 14:57, Cursitor Doom wrote:
>>>>> On Sat, 21 Dec 2024 08:57:51 +0000, liz@poppyrecords.invalid.invalid
>>>>> (Liz Tuddenham) wrote:
>>>>>
>>>>>> Cursitor Doom <cd@notformail.com> wrote:
>>>>>>
>>>>>>> On Sat, 21 Dec 2024 00:05:08 +0100, Jeroen Belleman
>>>>>>> <jeroen@nospam.please> wrote:
>>>>>>>
>>>>>>>> On 12/20/24 22:16, Cursitor Doom wrote:
>>>>>>>>> On Fri, 20 Dec 2024 19:32:14 +0000, liz@poppyrecords.invalid.invalid
>>>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>>>
>>>>>>>>>> Cursitor Doom <cd@notformail.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> Do we have any French speakers on the Panel? I have a radio that's
>>>>>>>>>>> badly in need of realignment and the only instructions I can find are
>>>>>>>>>>> a set in French. I can't use Google translate because they've used too
>>>>>>>>>>> many abbreviations in the text and they won't parse any sense.
>>>>>>>>>>
>>>>>>>>>> I'm not a particularly fluent French speaker, but I could probably sort
>>>>>>>>>> out some technical instructions in French If you want to send them to
>>>>>>>>>> me, I'll have a go (you should be able to work out my e-mail address).
>>>>>>>>>
>>>>>>>>> Many thanks indeed for your kind offer. I suspect it will probably
>>>>>>>>> require a native French speaker to decypher, but who knows? :-)
>>>>>>>>
>>>>>>>> I'm not a native French speaker, but I may be able to help anyway.
>>>>>>>> Fire away.
>>>>>>>
>>>>>>> Well that's interesing as I had did think you might respond given some
>>>>>>> of the background you've revealed here in the past. I don't have the
>>>>>>> relevant page here right now, but will make it available tomorrow. It
>>>>>>> is only the one page and only one column of that, so nothing too
>>>>>>> onerous. I did show it to a genuine French chum of mine a few weeks
>>>>>>> ago, but he was stumped by the technical side of it and couldn't
>>>>>>> assist much, unfortunately. So it appears it needs someone who can
>>>>>>> speak French fluently *and* understands the process of radio
>>>>>>> alignment. I kind of guessed that might be you....
>>>>>>
>>>>>>
>>>>>> Many years ago Practical Wireless published an article about the French
>>>>>> 819-line high-definition television service which had been translated
>>>>> >from French by someone who knew nothing about television or radio
>>>>>> terminologyy. It was hilarious nonsense but I eventually managed to
>>>>>> translate it back into French so that I could understand it.
>>>>>>
>>>>>> If you post your text here, we can all have a go at it.
>>>>>
>>>>> Sorry for the delay; took a bit of tracking down but I have it now:
>>>>>
>>>>> https://disk.yandex.com/i/3SiZ6rN_k-fP4w
>>>>>
>>>>> It's only page 1 that needs the translation - and of that, in
>>>>> particular the abbreviated bits. I haven't read French since I was in
>>>>> school about a hundred years ago, so it's all Dutch to me. :-)
>>>>
>>>>
>>>> This was translated from German into French by someone who also
>>>> did not know clearly what it all meant. Not everything makes
>>>> perfect sense.
>>>>
>>>> Also, while it doesn't say so, many of the adjustments interact,
>>>> so you may have to go back and forth a few times. Anyway, here
>>>> goes.
>>>>
>>>> Jeroen Belleman
>>>>
>>>>
>>>> ===============================================================
>>>>
>>>> -- DC current adjustments (for 9V supply)
>>>> - Adjustment of the push-pull audio stage:
>>>> Cut the solder bridge marked -x- in the collector trace of the
>>>> AC188 T11 and insert a current meter. Adjust R410 for 6.5mA.
>>>> Restore the bridge.
>>>> - Adjustment of the IF amplifier:
>>>> Set R515 to obtain 1.35V across T4's emitter resistor R518.
>>>>
>>>> -- Adjustment of the FM-IF stages. The radio should be set to "FM".
>>>> Connect a wobbulator centered on 10.7MHz at MP5 and the diode
>>>> detector shown at ZF VII (I think...) MP6. Detune ZF VIII (a).
>>>> Then tune ZFVII (b) for a symmetrical maximum response.
>>>> - Inject signal at MP3 and tune ZF VI (c) and ZF V (d) for
>>>> symmetrical maximum response.
>>>> - Inject signal on MP2 and adjust ZF IV (e) and ZF III (f) for
>>>> symmetrical maximum response.
>>>> - Inject a weakly coupled signal at the mixer (MP1?) and adjust
>>>> ZF II (g) and ZF I (h) for symmetrical maximum response.
>>>> - Discriminator: Inject signal at MP5, with a level low
>>>> enough that no limiting occurs in the IF strip. Observe the
>>>> signal at MP11 (audio amplifier input) with load impedance 50k.
>>>> Adjust ZF VIII (a) for symmetrical response.
>>>>
>>>> -- Adjustment of the AM IF (460kHz) stages. The radio should be
>>>> set to "PO" (AM, 560-1450kHz). Connect a measurement instrument
>>>> at MP4 (Weakly coupled).
>>>> - Inject a wobbulator signal at MP3 and adjust ZF XIII and ZF XII
>>>> for symmetrical maximum response.
>>>> - Inject signal at MP8 and adjust ZF XI for symmetrical maximum
>>>> response.
>>>> - Inject signal at MP7 and adjust ZF X and ZF IX for symmetrical
>>>> maximum response.
>>>>
>>>> -- Adjustment of local oscillator and AM input. For short and
>>>> medium wave, couple signal into the ferrite rod antenna using
>>>> the frame. For short wave, remove the rod antenna and couple
>>>> signal at the antenna connection through 15pF.
>>>> Tune to 560kHz and adjust (1) and (3) for maximum response.
>>>> Mixer sensitivity 13uV and oscillator output 60-90mV.
>>>> Tune to 1450 kHz and adjust (2) and (4) for maximum response.
>>>> - Set the radio to GO (Long wave, 160-240kHz).
>>>> Tune to 160kHz and adjust (5) and (6) for maximum response.
>>>> Mixer sensitivity 13uV and oscillator output 65-95mV.
>>>> - Set the radio to OC (Short wave, 6.5-15MHz)
>>>> Tune to 6.5MHz and adjust (8) and (10) for maximum response.
>>>> Tune to 15MHz and adjust (9) and (11) for maximum response.
>>>> Mixer sensitivity 5uV and oscillator output 35-90mV.
>>>>
>>>> -- Adjustment of the FM LO. Signal from an RF generator with
>>>> 60 Ohm output impedance injected directly at the mixer (MP1?)
>>>> with a loaded signal level <2mV. Set the radio to FM.
>>>> - Tune to 88MHz and adjust (A) and (C) for maximum response.
>>>> - Tune to 106MHz and adjust (B) and (D) for maximum response,
>>>> Noise level is about 5 times kT0. Oscillator output voltage
>>>> 75-85mV (at T2's emitter).
>>>
>>> It is interesting to compare the different approaches Jeroen and I have
>>> taken. Although we began with exactly the same source material, we have
>>> produced two markedly different ways of saying the same thing.
>>
>> Well, the important thing is that you agree on the key points.
>> Now it just so happens I have a vintage wobbulator (made by Knight
>> IIRC) which would be ideal for this job. It hasn't been used for about
>> 20 years so it'll probably explode at switch-on, but that's nothing
>> unusual around here as my neighbours will attest.
>
>I went back and forth between the text and the schematics to
>try and clear up some inaccuracies in the text. Comparing with
>the original German text, the G->F translator did an honourable
>job, in fact.

On 12/22/2024 8:27 AM, Cursitor Doom wrote:
> On Sun, 22 Dec 2024 12:37:37 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
>
>> Jeroen Belleman <jeroen@nospam.please> wrote:
>>
>>> On 12/21/24 14:57, Cursitor Doom wrote:
>>>> On Sat, 21 Dec 2024 08:57:51 +0000, liz@poppyrecords.invalid.invalid
>>>> (Liz Tuddenham) wrote:
>>>>
>>>>> Cursitor Doom <cd@notformail.com> wrote:
>>>>>
>>>>>> On Sat, 21 Dec 2024 00:05:08 +0100, Jeroen Belleman
>>>>>> <jeroen@nospam.please> wrote:
>>>>>>
>>>>>>> On 12/20/24 22:16, Cursitor Doom wrote:
>>>>>>>> On Fri, 20 Dec 2024 19:32:14 +0000, liz@poppyrecords.invalid.invalid
>>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>>
>>>>>>>>> Cursitor Doom <cd@notformail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Do we have any French speakers on the Panel? I have a radio that's
>>>>>>>>>> badly in need of realignment and the only instructions I can find are
>>>>>>>>>> a set in French. I can't use Google translate because they've used too
>>>>>>>>>> many abbreviations in the text and they won't parse any sense.
>>>>>>>>>
>>>>>>>>> I'm not a particularly fluent French speaker, but I could probably sort
>>>>>>>>> out some technical instructions in French If you want to send them to
>>>>>>>>> me, I'll have a go (you should be able to work out my e-mail address).
>>>>>>>>
>>>>>>>> Many thanks indeed for your kind offer. I suspect it will probably
>>>>>>>> require a native French speaker to decypher, but who knows? :-)
>>>>>>>
>>>>>>> I'm not a native French speaker, but I may be able to help anyway.
>>>>>>> Fire away.
>>>>>>
>>>>>> Well that's interesing as I had did think you might respond given some
>>>>>> of the background you've revealed here in the past. I don't have the
>>>>>> relevant page here right now, but will make it available tomorrow. It
>>>>>> is only the one page and only one column of that, so nothing too
>>>>>> onerous. I did show it to a genuine French chum of mine a few weeks
>>>>>> ago, but he was stumped by the technical side of it and couldn't
>>>>>> assist much, unfortunately. So it appears it needs someone who can
>>>>>> speak French fluently *and* understands the process of radio
>>>>>> alignment. I kind of guessed that might be you....
>>>>>
>>>>>
>>>>> Many years ago Practical Wireless published an article about the French
>>>>> 819-line high-definition television service which had been translated
>>>> >from French by someone who knew nothing about television or radio
>>>>> terminologyy. It was hilarious nonsense but I eventually managed to
>>>>> translate it back into French so that I could understand it.
>>>>>
>>>>> If you post your text here, we can all have a go at it.
>>>>
>>>> Sorry for the delay; took a bit of tracking down but I have it now:
>>>>
>>>> https://disk.yandex.com/i/3SiZ6rN_k-fP4w
>>>>
>>>> It's only page 1 that needs the translation - and of that, in
>>>> particular the abbreviated bits. I haven't read French since I was in
>>>> school about a hundred years ago, so it's all Dutch to me. :-)
>>>
>>>
>>> This was translated from German into French by someone who also
>>> did not know clearly what it all meant. Not everything makes
>>> perfect sense.
>>>
>>> Also, while it doesn't say so, many of the adjustments interact,
>>> so you may have to go back and forth a few times. Anyway, here
>>> goes.
>>>
>>> Jeroen Belleman
>>>
>>>
>>> ===============================================================
>>>
>>> -- DC current adjustments (for 9V supply)
>>> - Adjustment of the push-pull audio stage:
>>> Cut the solder bridge marked -x- in the collector trace of the
>>> AC188 T11 and insert a current meter. Adjust R410 for 6.5mA.
>>> Restore the bridge.
>>> - Adjustment of the IF amplifier:
>>> Set R515 to obtain 1.35V across T4's emitter resistor R518.
>>>
>>> -- Adjustment of the FM-IF stages. The radio should be set to "FM".
>>> Connect a wobbulator centered on 10.7MHz at MP5 and the diode
>>> detector shown at ZF VII (I think...) MP6. Detune ZF VIII (a).
>>> Then tune ZFVII (b) for a symmetrical maximum response.
>>> - Inject signal at MP3 and tune ZF VI (c) and ZF V (d) for
>>> symmetrical maximum response.
>>> - Inject signal on MP2 and adjust ZF IV (e) and ZF III (f) for
>>> symmetrical maximum response.
>>> - Inject a weakly coupled signal at the mixer (MP1?) and adjust
>>> ZF II (g) and ZF I (h) for symmetrical maximum response.
>>> - Discriminator: Inject signal at MP5, with a level low
>>> enough that no limiting occurs in the IF strip. Observe the
>>> signal at MP11 (audio amplifier input) with load impedance 50k.
>>> Adjust ZF VIII (a) for symmetrical response.
>>>
>>> -- Adjustment of the AM IF (460kHz) stages. The radio should be
>>> set to "PO" (AM, 560-1450kHz). Connect a measurement instrument
>>> at MP4 (Weakly coupled).
>>> - Inject a wobbulator signal at MP3 and adjust ZF XIII and ZF XII
>>> for symmetrical maximum response.
>>> - Inject signal at MP8 and adjust ZF XI for symmetrical maximum
>>> response.
>>> - Inject signal at MP7 and adjust ZF X and ZF IX for symmetrical
>>> maximum response.
>>>
>>> -- Adjustment of local oscillator and AM input. For short and
>>> medium wave, couple signal into the ferrite rod antenna using
>>> the frame. For short wave, remove the rod antenna and couple
>>> signal at the antenna connection through 15pF.
>>> Tune to 560kHz and adjust (1) and (3) for maximum response.
>>> Mixer sensitivity 13uV and oscillator output 60-90mV.
>>> Tune to 1450 kHz and adjust (2) and (4) for maximum response.
>>> - Set the radio to GO (Long wave, 160-240kHz).
>>> Tune to 160kHz and adjust (5) and (6) for maximum response.
>>> Mixer sensitivity 13uV and oscillator output 65-95mV.
>>> - Set the radio to OC (Short wave, 6.5-15MHz)
>>> Tune to 6.5MHz and adjust (8) and (10) for maximum response.
>>> Tune to 15MHz and adjust (9) and (11) for maximum response.
>>> Mixer sensitivity 5uV and oscillator output 35-90mV.
>>>
>>> -- Adjustment of the FM LO. Signal from an RF generator with
>>> 60 Ohm output impedance injected directly at the mixer (MP1?)
>>> with a loaded signal level <2mV. Set the radio to FM.
>>> - Tune to 88MHz and adjust (A) and (C) for maximum response.
>>> - Tune to 106MHz and adjust (B) and (D) for maximum response,
>>> Noise level is about 5 times kT0. Oscillator output voltage
>>> 75-85mV (at T2's emitter).
>>
>> It is interesting to compare the different approaches Jeroen and I have
>> taken. Although we began with exactly the same source material, we have
>> produced two markedly different ways of saying the same thing.
>
> Well, the important thing is that you agree on the key points.
> Now it just so happens I have a vintage wobbulator (made by Knight
> IIRC) which would be ideal for this job. It hasn't been used for about
> 20 years so it'll probably explode at switch-on, but that's nothing
> unusual around here as my neighbours will attest.

Maybe you should first build a dim bulb tester. Among other
things, it would enable you to re-form the power supply caps
it old gear and save an explosion or three. :-)

Many hits on a Google search, here's the first one:
https://antiqueradio.org/dimbulb.htm

On Sun, 22 Dec 2024 12:57:54 -0500, ehsjr <ehsjr@verizon.net> wrote:

>
>Maybe you should first build a dim bulb tester. Among other
>things, it would enable you to re-form the power supply caps
>it old gear and save an explosion or three. :-)
>
>Many hits on a Google search, here's the first one:
>https://antiqueradio.org/dimbulb.htm
>
>Ed

I did actually build one a few years ago with swappable bulbs for
different loads. Two problems, though:

1) I'd have to remember to use it
2) I'd have to somehow find it.

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
> Cursitor Doom <cd@notformail.com> wrote:
>
>> On 21 Dec 2024 22:30:23 GMT, Allodoxaphobia <trepidation@example.net>
>> wrote:
>>
>>> On Sat, 21 Dec 2024 21:37:59 +0000, Cursitor Doom wrote:
>>>>> in series with your 50 Ohm source.
>>>>
>>>> Yes, but you know what a *bitch* it is to find a purely resistive 10
>>>> ohms....
>>>
>>> Maybe just a length of nichrome wire?
>>
>> Still got parasitics. Avoiding them is a craft in itself.
>
> I wouldn't worry about the inductance of an ordianry 1/4 -Watt resistor
> at the frequencies involved. The only point where it might make any
> difference is the VHF input and oscillator tuning - and I can't think
> you need a great level of accuracy to align a domestic portable radio.
>
> It is even possible that they specified a 60-ohm sig gen because they
> knew that most of the available ones would be near enough at either 50
> or 75 0hms. Another possibility would be to try to make you think you
> had to return the radio to their specialised service department for
> repair. The avarage radio shop (if there are any left) simply wouldn't
> care and would use whatever they had on the shelf above the workbench.
>
>

60 ohms was a popular impedance for RF test gear in Europe in the 1950s and
60s

--
piglet

On 22/12/2024 22:50, Cursitor Doom wrote:
> On Sun, 22 Dec 2024 12:57:54 -0500, ehsjr <ehsjr@verizon.net> wrote:
>
>>
>> Maybe you should first build a dim bulb tester. Among other
>> things, it would enable you to re-form the power supply caps
>> it old gear and save an explosion or three. :-)
>>
>> Many hits on a Google search, here's the first one:
>> https://antiqueradio.org/dimbulb.htm
>>
>> Ed
>
> I did actually build one a few years ago with swappable bulbs for
> different loads. Two problems, though:
>
> 1) I'd have to remember to use it
> 2) I'd have to somehow find it.

I think that you might have to add a third one in future - finding an
incandescent bulb to use!

--
Jeff

On Mon, 23 Dec 2024 08:16:15 +0000, Jeff Layman <Jeff@invalid.invalid>
wrote:

>On 22/12/2024 22:50, Cursitor Doom wrote:
>> On Sun, 22 Dec 2024 12:57:54 -0500, ehsjr <ehsjr@verizon.net> wrote:
>>
>>>
>>> Maybe you should first build a dim bulb tester. Among other
>>> things, it would enable you to re-form the power supply caps
>>> it old gear and save an explosion or three. :-)
>>>
>>> Many hits on a Google search, here's the first one:
>>> https://antiqueradio.org/dimbulb.htm
>>>
>>> Ed
>>
>> I did actually build one a few years ago with swappable bulbs for
>> different loads. Two problems, though:
>>
>> 1) I'd have to remember to use it
>> 2) I'd have to somehow find it.
>
>I think that you might have to add a third one in future - finding an
>incandescent bulb to use!

Yes, getting harder as time goes by, so I stocked-up in advance and
put a couple of dozen aside while they were still widely available. I
would imagine the oven types will still be around for a few more
years, anyway - and they tend to be more robust.

In message <vka5ni$r5r3$1@dont-email.me>, piglet
<erichpwagner@hotmail.com> writes
>Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
>> Cursitor Doom <cd@notformail.com> wrote:
>>
>>> On 21 Dec 2024 22:30:23 GMT, Allodoxaphobia <trepidation@example.net>
>>> wrote:
>>>
>>>> On Sat, 21 Dec 2024 21:37:59 +0000, Cursitor Doom wrote:
>>>>>> in series with your 50 Ohm source.
>>>>>
>>>>> Yes, but you know what a *bitch* it is to find a purely resistive 10
>>>>> ohms....
>>>>
>>>> Maybe just a length of nichrome wire?
>>>
>>> Still got parasitics. Avoiding them is a craft in itself.
>>
>> I wouldn't worry about the inductance of an ordianry 1/4 -Watt resistor
>> at the frequencies involved. The only point where it might make any
>> difference is the VHF input and oscillator tuning - and I can't think
>> you need a great level of accuracy to align a domestic portable radio.
>>
>> It is even possible that they specified a 60-ohm sig gen because they
>> knew that most of the available ones would be near enough at either 50
>> or 75 0hms. Another possibility would be to try to make you think you
>> had to return the radio to their specialised service department for
>> repair. The avarage radio shop (if there are any left) simply wouldn't
>> care and would use whatever they had on the shelf above the workbench.
>>
>60 ohms was a popular impedance for RF test gear in Europe in the 1950s and
>60s
>
For many purposes you can ignore the difference between the 50 and 75
ohm impedances (and 60 if you ever come across any). However, be very
aware only BNC 50 and 75 ohm connectors are mutually mechanically
mateable (yes - they really are!). I don't know if any others that are.
--
Ian
Aims and ambitions are neither attainments nor achievements

On 2024-12-23 16:22, Ian Jackson wrote:
> For many purposes you can ignore the difference between the 50 and 75 ohm impedances (and 60 if you ever come across any).
> However, be very aware only BNC 50 and 75 ohm connectors are mutually mechanically mateable (yes - they really are!). I don't know if any others that are.

Not recommended.
The center pin differs, a 50 Ohm BNC pin is thicker and may damage a 75 ohm BNC.
I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV company), the rest is 50.

Arie

In article <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, noreply@ademu.nl
says...
>
> On 2024-12-23 16:22, Ian Jackson wrote:
> > For many purposes you can ignore the difference between the 50 and 75 ohm impedances (and 60 if you ever come across any).
> > However, be very aware only BNC 50 and 75 ohm connectors are mutually mechanically mateable (yes - they really are!). I don't know if any others that are.
>
> Not recommended.
> The center pin differs, a 50 Ohm BNC pin is thicker and may damage a 75 ohm BNC.
> I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV company), the rest is 50.
>
>
>

It is the N connector the center pin is different. The BNC pin is the
same. It is the ammount of dialectric (insulation) in the BNC that
makes it a 75 or 50 ohm connector.

On 12/23/24 18:58, Ralph Mowery wrote:
> In article <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, noreply@ademu.nl
> says...
>>
>> On 2024-12-23 16:22, Ian Jackson wrote:
>>> For many purposes you can ignore the difference between the 50 and 75 ohm impedances (and 60 if you ever come across any).
>>> However, be very aware only BNC 50 and 75 ohm connectors are mutually mechanically mateable (yes - they really are!). I don't know if any others that are.
>>
>> Not recommended.
>> The center pin differs, a 50 Ohm BNC pin is thicker and may damage a 75 ohm BNC.
>> I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV company), the rest is 50.
>>
>>
>>
>
> It is the N connector the center pin is different. The BNC pin is the
> same. It is the ammount of dialectric (insulation) in the BNC that
> makes it a 75 or 50 ohm connector.
>
>

N connectors are good, but the fact that 75 and 50 Ohm connectors
are similar enough to mate, but not nearly enough to do so without
damage or malfunction is perverse. When I took charge of the
electronics lab, it took a while to sort them out and to eliminate
the victims of mismatched matings. (I was always amazed at the
sheer quantity of connectors in a busy lab.)

For BNCs, there *is* a difference, but it doesn't usually matter.
I kept 50 and 75 Ohms separate, but when put to the test, many
75 Ohm connectors turned out to really be 50 Ohm ones in disguise.

In a pinch, BNC and N can even mate between them. I'm not sure if
that's deliberate or accidental.

Jeroen Belleman

In message <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, Arie de Muijnck
<noreply@ademu.nl> writes
>On 2024-12-23 16:22, Ian Jackson wrote:
>> For many purposes you can ignore the difference between the 50 and 75
>>ohm impedances (and 60 if you ever come across any). However, be very
>>aware only BNC 50 and 75 ohm connectors are mutually mechanically
>>mateable (yes - they really are!). I don't know if any others that are.
>
>Not recommended.
>The center pin differs, a 50 Ohm BNC pin is thicker and may damage a 75
>ohm BNC.
>I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV
>company), the rest is 50.
>
For most of its length, the male BNC 50 ohm pin is actually the same
diameter as the 75. However, the tip of the 50 pin is fairly 'blunt',
while the 75 is more pointed.

I guess that if you are particularly clumsy while you are inserting a 50
male into a female 75, it might just be possible to have the blunter
male pin a bit off-centre, and catch the side of the female receptacle,
and splay it. However, despite 43 years working in the CATV industry, I
failed to achieve this!

The real difference between the two impedances is that the amount of
PTFE dielectric in the 75 has been minimised in order to increase (with
some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
more-uniform structural RLR, so it the better connector at the higher
frequencies.
--
Ian
Aims and ambitions are neither attainments nor achievements

In message <MPG.41d36ed7f88483b798a01a@news.eternal-september.org>,
Ralph Mowery <rmowery42@charter.net> writes
>In article <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, noreply@ademu.nl
>says...
>>
>> On 2024-12-23 16:22, Ian Jackson wrote:
>> > For many purposes you can ignore the difference between the 50 and
>> >75 ohm impedances (and 60 if you ever come across any).
>> > However, be very aware only BNC 50 and 75 ohm connectors are
>> >mutually mechanically mateable (yes - they really are!). I don't
>> >know if any others that are.
>>
>> Not recommended.
>> The center pin differs, a 50 Ohm BNC pin is thicker and may damage a
>>75 ohm BNC.
>> I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV
>>company), the rest is 50.
>>
>>
>>
>
>It is the N connector the center pin is different.

Indeed. A 75 ohm N male (thin pin) inserted into a 50 ohm female
(fatter receptacle) results in a non-connection. A 50 ohm N male (fat
pin) inserted into a 75 ohm female (thin receptacle) results in a
splayed (and usually wrecked for future use) receptacle.

> The BNC pin is the
>same. It is the ammount of dialectric (insulation) in the BNC that
>makes it a 75 or 50 ohm connector.
--
Ian
Aims and ambitions are neither attainments nor achievements

In message <vkckph$1cvdj$1@dont-email.me>, Jeroen Belleman
<jeroen@nospam.please> writes
>On 12/23/24 18:58, Ralph Mowery wrote:
>> In article <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, noreply@ademu.nl
>> says...
>>>
>>> On 2024-12-23 16:22, Ian Jackson wrote:
>>>> For many purposes you can ignore the difference between the 50 and
>>>>75 ohm impedances (and 60 if you ever come across any).
>>>> However, be very aware only BNC 50 and 75 ohm connectors are
>>>>mutually mechanically mateable (yes - they really are!). I don't
>>>>know if any others that are.
>>>
>>> Not recommended.
>>> The center pin differs, a 50 Ohm BNC pin is thicker and may damage a
>>>75 ohm BNC.
>>> I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV
>>>company), the rest is 50.
>>>
>>>
>>>
>> It is the N connector the center pin is different. The BNC pin is
>>the
>> same. It is the ammount of dialectric (insulation) in the BNC that
>> makes it a 75 or 50 ohm connector.
>>
>
>N connectors are good, but the fact that 75 and 50 Ohm connectors
>are similar enough to mate, but not nearly enough to do so without
>damage or malfunction is perverse. When I took charge of the
>electronics lab, it took a while to sort them out and to eliminate
>the victims of mismatched matings. (I was always amazed at the
>sheer quantity of connectors in a busy lab.)
>
>For BNCs, there *is* a difference, but it doesn't usually matter.
>I kept 50 and 75 Ohms separate, but when put to the test, many
>75 Ohm connectors turned out to really be 50 Ohm ones in disguise.
>
>In a pinch, BNC and N can even mate between them. I'm not sure if
>that's deliberate or accidental.
>
Yes - the 'innards' are essentially the same. IIRC, the BNC innards also
mate with C-connectors. I think it's deliberate. After all, its the
innards that carry the RF.
--
Ian
Aims and ambitions are neither attainments nor achievements

On Mon, 23 Dec 2024 23:05:03 +0000, Ian Jackson
<ianREMOVETHISjackson@g3ohx.co.uk> wrote:

>The real difference between the two impedances is that the amount of
>PTFE dielectric in the 75 has been minimised in order to increase (with
>some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
>more-uniform structural RLR, so it the better connector at the higher
>frequencies.

I don't think that's quite right. The diameter of the inner and outer
conductors has more influence on Zo than the dilectric thickness.

Ian Jackson <ianREMOVETHISjackson@g3ohx.co.uk> wrote:
> In message <vkckph$1cvdj$1@dont-email.me>, Jeroen Belleman
> <jeroen@nospam.please> writes
>> On 12/23/24 18:58, Ralph Mowery wrote:
>>> In article <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, noreply@ademu.nl
>>> says...
>>>>
>>>> On 2024-12-23 16:22, Ian Jackson wrote:
>>>>> For many purposes you can ignore the difference between the 50 and
>>>>> 75 ohm impedances (and 60 if you ever come across any).
>>>>> However, be very aware only BNC 50 and 75 ohm connectors are
>>>>> mutually mechanically mateable (yes - they really are!). I don't
>>>>> know if any others that are.
>>>>
>>>> Not recommended.
>>>> The center pin differs, a 50 Ohm BNC pin is thicker and may damage a
>>>> 75 ohm BNC.
>>>> I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV
>>>> company), the rest is 50.
>>>>
>>>>
>>>>
>>> It is the N connector the center pin is different. The BNC pin is
>>> the
>>> same. It is the ammount of dialectric (insulation) in the BNC that
>>> makes it a 75 or 50 ohm connector.
>>>
>>
>> N connectors are good, but the fact that 75 and 50 Ohm connectors
>> are similar enough to mate, but not nearly enough to do so without
>> damage or malfunction is perverse. When I took charge of the
>> electronics lab, it took a while to sort them out and to eliminate
>> the victims of mismatched matings. (I was always amazed at the
>> sheer quantity of connectors in a busy lab.)
>>
>> For BNCs, there *is* a difference, but it doesn't usually matter.
>> I kept 50 and 75 Ohms separate, but when put to the test, many
>> 75 Ohm connectors turned out to really be 50 Ohm ones in disguise.
>>
>> In a pinch, BNC and N can even mate between them. I'm not sure if
>> that's deliberate or accidental.
>>
> Yes - the 'innards' are essentially the same. IIRC, the BNC innards also
> mate with C-connectors. I think it's deliberate. After all, its the
> innards that carry the RF.

A type N male will also mate with a BNC female.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

On 23/12/2024 10:31, Cursitor Doom wrote:
> On Mon, 23 Dec 2024 08:16:15 +0000, Jeff Layman <Jeff@invalid.invalid>

>>> I did actually build one a few years ago with swappable bulbs for
>>> different loads. Two problems, though:
>>>
>>> 1) I'd have to remember to use it
>>> 2) I'd have to somehow find it.
>>
>> I think that you might have to add a third one in future - finding an
>> incandescent bulb to use!
>
> Yes, getting harder as time goes by, so I stocked-up in advance and
> put a couple of dozen aside while they were still widely available. I
> would imagine the oven types will still be around for a few more
> years, anyway - and they tend to be more robust.

I doubt they'll be able to replace the oven illumination easily (unless
they mount the bulb on the outside and use fibreoptics to bring light to
the inside!). I was surprised a few months ago when I bought a new
microwave oven to find it had an LED lamp which illuminated the inside.
I would have thought that with around a kW of microwave energy being
generated that would have been a pretty hostile environment for an LED
lamp. Obviously, though, they had the screening well sorted out. I
suppose that I shouldn't have been surprised as the timing and display
circuitry have been around for years and hasn't been affected by the RF
energy or switching spikes.

--
Jeff

In message <6ftjmjppf4421dl2ec0ek4mvfht74lmnu2@4ax.com>, Cursitor Doom
<cd@notformail.com> writes
>On Mon, 23 Dec 2024 23:05:03 +0000, Ian Jackson
><ianREMOVETHISjackson@g3ohx.co.uk> wrote:
>
>>The real difference between the two impedances is that the amount of
>>PTFE dielectric in the 75 has been minimised in order to increase (with
>>some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
>>more-uniform structural RLR, so it the better connector at the higher
>>frequencies.
>
>I don't think that's quite right. The diameter of the inner and outer
>conductors has more influence on Zo than the dilectric thickness.

It's right all right.

The outer diameter is the same for the 50 and 75 ohms. For the 75, I
presume it's not practicable to make the pin diameter smaller and retain
its robustness, so the only way to increase the Zo is to remove as much
of the dielectric as possible. If you compare the 50 and the 75, you
will see what I mean.
--
Ian
Aims and ambitions are neither attainments nor achievements

On Tue, 24 Dec 2024 22:42:17 +0000, Ian Jackson
<ianREMOVETHISjackson@g3ohx.co.uk> wrote:

>In message <6ftjmjppf4421dl2ec0ek4mvfht74lmnu2@4ax.com>, Cursitor Doom
><cd@notformail.com> writes
>>On Mon, 23 Dec 2024 23:05:03 +0000, Ian Jackson
>><ianREMOVETHISjackson@g3ohx.co.uk> wrote:
>>
>>>The real difference between the two impedances is that the amount of
>>>PTFE dielectric in the 75 has been minimised in order to increase (with
>>>some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
>>>more-uniform structural RLR, so it the better connector at the higher
>>>frequencies.
>>
>>I don't think that's quite right. The diameter of the inner and outer
>>conductors has more influence on Zo than the dilectric thickness.
>
>It's right all right.
>
>The outer diameter is the same for the 50 and 75 ohms. For the 75, I
>presume it's not practicable to make the pin diameter smaller and retain
>its robustness, so the only way to increase the Zo is to remove as much
>of the dielectric as possible. If you compare the 50 and the 75, you
>will see what I mean.

I still maintain the principal determinants of the impedance are as I
stated previously. The formulas for line impedance are shown on this
page and the aforementioned determinants are key.

https://www.everythingrf.com/rf-calculators/coaxial-cable-calculator

On Tue, 24 Dec 2024 10:13:29 +0000, Jeff Layman <Jeff@invalid.invalid>
wrote:

>On 23/12/2024 10:31, Cursitor Doom wrote:
>> On Mon, 23 Dec 2024 08:16:15 +0000, Jeff Layman <Jeff@invalid.invalid>
>
>>>> I did actually build one a few years ago with swappable bulbs for
>>>> different loads. Two problems, though:
>>>>
>>>> 1) I'd have to remember to use it
>>>> 2) I'd have to somehow find it.
>>>
>>> I think that you might have to add a third one in future - finding an
>>> incandescent bulb to use!
>>
>> Yes, getting harder as time goes by, so I stocked-up in advance and
>> put a couple of dozen aside while they were still widely available. I
>> would imagine the oven types will still be around for a few more
>> years, anyway - and they tend to be more robust.
>
>I doubt they'll be able to replace the oven illumination easily (unless
>they mount the bulb on the outside and use fibreoptics to bring light to
>the inside!). I was surprised a few months ago when I bought a new
>microwave oven to find it had an LED lamp which illuminated the inside.
>I would have thought that with around a kW of microwave energy being
>generated that would have been a pretty hostile environment for an LED
>lamp. Obviously, though, they had the screening well sorted out. I
>suppose that I shouldn't have been surprised as the timing and display
>circuitry have been around for years and hasn't been affected by the RF
>energy or switching spikes.

If they placed the LEDs in the corners of the inner cabinet then they
would be quite safe. All the RF energy is concentrated towards the
center with very little indeed misdirected.

On 12/25/24 15:48, Cursitor Doom wrote:
> On Tue, 24 Dec 2024 22:42:17 +0000, Ian Jackson
> <ianREMOVETHISjackson@g3ohx.co.uk> wrote:
>
>> In message <6ftjmjppf4421dl2ec0ek4mvfht74lmnu2@4ax.com>, Cursitor Doom
>> <cd@notformail.com> writes
>>> On Mon, 23 Dec 2024 23:05:03 +0000, Ian Jackson
>>> <ianREMOVETHISjackson@g3ohx.co.uk> wrote:
>>>
>>>> The real difference between the two impedances is that the amount of
>>>> PTFE dielectric in the 75 has been minimised in order to increase (with
>>>> some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
>>>> more-uniform structural RLR, so it the better connector at the higher
>>>> frequencies.
>>>
>>> I don't think that's quite right. The diameter of the inner and outer
>>> conductors has more influence on Zo than the dilectric thickness.
>>
>> It's right all right.
>>
>> The outer diameter is the same for the 50 and 75 ohms. For the 75, I
>> presume it's not practicable to make the pin diameter smaller and retain
>> its robustness, so the only way to increase the Zo is to remove as much
>> of the dielectric as possible. If you compare the 50 and the 75, you
>> will see what I mean.
>
> I still maintain the principal determinants of the impedance are as I
> stated previously. The formulas for line impedance are shown on this
> page and the aforementioned determinants are key.
>
> https://www.everythingrf.com/rf-calculators/coaxial-cable-calculator
>

Very poor web page indeed. No educational value whatever.

They lump together the values of the dieelectric constant
and the permeability of free space, the geometry of the
configuration and the conversion from natural to base-ten
logarithms all together into one magic factor, without any
hint of where it all came from.

Shame! That's not 'everythingRF': It's almost nothing!
Oh, and there is no such thing as "impedance per unit length".

Jeroen Belleman

In article <8i6omj1vidqoch9421207205iajrb0h5ue@4ax.com>,
cd@notformail.com says...
> will see what I mean.
>
> I still maintain the principal determinants of the impedance are as I
> stated previously. The formulas for line impedance are shown on this
> page and the aforementioned determinants are key.
>
> https://www.everythingrf.com/rf-calculators/coaxial-cable-calculator
>
>
>

I could not get the calculator to come out for me. Getting negative
numbers and about 10 times what they should be.

However if you change the Relative Permittivity you will see how much it
will effect the impedance of the coax. Go from 1 as air and then 2.1 to
2.6 for teflon and other common insulator/dialectric material and see
how much the impedance changes.

I doubt that you have ever actually ran the numbers or you would see the
impedance change as the material is changed.

The main thing is the ratio of the diameters of the cables, but you
still have to account for the material between them just as you will for
a capacitor..

You can often find the Relative Permittivity tables where capacitors
are.

On Mon, 23 Dec 2024 23:05:03 +0000, Ian Jackson
<ianREMOVETHISjackson@g3ohx.co.uk> wrote:

>In message <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, Arie de Muijnck
><noreply@ademu.nl> writes
>>On 2024-12-23 16:22, Ian Jackson wrote:
>>> For many purposes you can ignore the difference between the 50 and 75
>>>ohm impedances (and 60 if you ever come across any). However, be very
>>>aware only BNC 50 and 75 ohm connectors are mutually mechanically
>>>mateable (yes - they really are!). I don't know if any others that are.
>>
>>Not recommended.
>>The center pin differs, a 50 Ohm BNC pin is thicker and may damage a 75
>>ohm BNC.
>>I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV
>>company), the rest is 50.
>>
>For most of its length, the male BNC 50 ohm pin is actually the same
>diameter as the 75. However, the tip of the 50 pin is fairly 'blunt',
>while the 75 is more pointed.
>
>I guess that if you are particularly clumsy while you are inserting a 50
>male into a female 75, it might just be possible to have the blunter
>male pin a bit off-centre, and catch the side of the female receptacle,
>and splay it. However, despite 43 years working in the CATV industry, I
>failed to achieve this!
>
>The real difference between the two impedances is that the amount of
>PTFE dielectric in the 75 has been minimised in order to increase (with
>some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
>more-uniform structural RLR, so it the better connector at the higher
>frequencies.

The critical part of the connector here is a fraction of an inch long,
so none of this stuff matters below a few GHz.

On Wed, 25 Dec 2024 13:40:19 -0500, Ralph Mowery
<rmowery42@charter.net> wrote:

>In article <8i6omj1vidqoch9421207205iajrb0h5ue@4ax.com>,
>cd@notformail.com says...
>> will see what I mean.
>>
>> I still maintain the principal determinants of the impedance are as I
>> stated previously. The formulas for line impedance are shown on this
>> page and the aforementioned determinants are key.
>>
>> https://www.everythingrf.com/rf-calculators/coaxial-cable-calculator
>>
>>
>>
>
>I could not get the calculator to come out for me. Getting negative
>numbers and about 10 times what they should be.

There are a lot of silly equations around, that people plug into apps.

Try a wide microstrip in some online calculators. Many use the
equation that's in the old Motorola ECL book, and a wide trace reports
a negative Z.

In message <l7vomj55u59o3cu753v7de77t0j4n20jtp@4ax.com>, john larkin
<JL@gct.com> writes
>On Mon, 23 Dec 2024 23:05:03 +0000, Ian Jackson
><ianREMOVETHISjackson@g3ohx.co.uk> wrote:
>
>>In message <nnd$23e91f0d$053bf96e@d25fd620e9918bf1>, Arie de Muijnck
>><noreply@ademu.nl> writes
>>>On 2024-12-23 16:22, Ian Jackson wrote:
>>>> For many purposes you can ignore the difference between the 50 and 75
>>>>ohm impedances (and 60 if you ever come across any). However, be very
>>>>aware only BNC 50 and 75 ohm connectors are mutually mechanically
>>>>mateable (yes - they really are!). I don't know if any others that are.
>>>
>>>Not recommended.
>>>The center pin differs, a 50 Ohm BNC pin is thicker and may damage a 75
>>>ohm BNC.
>>>I'm cautious, most of my below 1 GHz equipment is 75 Ohms (from CATV
>>>company), the rest is 50.
>>>
>>For most of its length, the male BNC 50 ohm pin is actually the same
>>diameter as the 75. However, the tip of the 50 pin is fairly 'blunt',
>>while the 75 is more pointed.
>>
>>I guess that if you are particularly clumsy while you are inserting a 50
>>male into a female 75, it might just be possible to have the blunter
>>male pin a bit off-centre, and catch the side of the female receptacle,
>>and splay it. However, despite 43 years working in the CATV industry, I
>>failed to achieve this!
>>
>>The real difference between the two impedances is that the amount of
>>PTFE dielectric in the 75 has been minimised in order to increase (with
>>some difficulty) the Zo from 50 to 75 ohms. IIRC, the 50 has a
>>more-uniform structural RLR, so it the better connector at the higher
>>frequencies.
>
>The critical part of the connector here is a fraction of an inch long,
>so none of this stuff matters below a few GHz.

Yes. Obviously.
I've been retired now for many a year but, IIRC, the 50 ohm was
considered 'good' to around 1000 MHz, and the 75 to around 500MHz. [A
Google on the individual manufacturers' specs is recommended.]
Regardless, both are often used to higher frequencies.
>

--
Ian
Aims and ambitions are neither attainments nor achievements