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 Post subject: Frequency counter
PostPosted: May Mon 16, 2022 3:38 pm 
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Joined: Feb Thu 19, 2015 12:49 pm
Posts: 125
I built Daves dual 6C4 sw,the radio board site which is now shutdown. I would like go hook up a counter to know where I am tuning. Sometimes it takes a long time for station ID especially the foreign stations and I don't want to listen that long to someone I can't understand. Any ideas?


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 Post subject: Re: Frequency counter
PostPosted: May Mon 16, 2022 4:02 pm 
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Joined: May Tue 30, 2006 3:46 pm
Posts: 11458
Location: Santa Rosa, CA
If it's this one... any place you connect the freq. counter will change the received frequency.

Image

You can try connecting to the top of the 250 pF variable cap, but that might cause the signal to change or drop out.

Rich


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 Post subject: Re: Frequency counter
PostPosted: May Mon 16, 2022 4:06 pm 
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Joined: May Tue 30, 2006 3:46 pm
Posts: 11458
Location: Santa Rosa, CA
If you have a signal generator, you could use that to "zero-beat" and spot your frequency pretty closely.

Depending on the tuning range of your receiver, you could also try to find known strong signals, like WWV. They will also tell you the exact time.

Rich


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 Post subject: Re: Frequency counter
PostPosted: May Mon 16, 2022 5:56 pm 
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Joined: Jun Sun 15, 2014 4:37 pm
Posts: 2118
Location: Montreal, Quebec
A regen only generates a signal when oscillating. So nothing for a frequency counter to read otherwise.


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 Post subject: Re: Frequency counter
PostPosted: May Mon 16, 2022 6:21 pm 
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Joined: Jul Fri 18, 2008 9:02 am
Posts: 2621
Location: Alton IL 62002 Near ST. Louis
A digital tracking radio would also work .

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 Post subject: Re: Frequency counter
PostPosted: May Tue 17, 2022 1:14 pm 
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Joined: Jan Wed 15, 2020 11:29 pm
Posts: 2181
Location: AUSTRALIA
Location: Queensland.
You can count the incoming tuned carrier, if the counter is sensitive enough, disagreeing with what mblack said.

One of the very best frequency counters to add to a radio, as an "add-on" was made by CCI. It came as a kit, see this thread:

https://antiqueradios.com/forums/viewto ... 8&t=394544

There is enough data there to build one.

You can configure it to measure frequency directly, or measure the L/O in a superhet radio with an offset equal to the IF frequency.

It was very sensitive at its input, but I also added an input pre-amp to make it work on a sniff of signal of a small fraction of a millivolt with very low coupling, so it wouldn't affect the circuit being monitored.

There are now lots of frequency counter modules on ebay with uP's that look like good value, but none are as good as this old CCI counter, and most require a substantial input voltage > than a few hundred millivolts pp to count reliably.

In between these two extremes of a modern firmware based counter with a uP, and a counter based on plain digital logic IC's (like CCI's counter) is a single chip counter, dedicated for the task. Basically these are digital logic all in one package with the LED display drivers in there.

Intersil specialized in these counter IC's, a typical example being the ICM7208, which greatly simplified making a counter, these where used in Philips RF generators that went to 125MHz, for example the model PM5326:

https://www.semiee.com/file/EOL2/Intersil-ICM7208.pdf

These are dead easy to use (but for your application would require a pre-amp), I collected many of these IC's years ago as I could see the beauty of them, and they are mostly superior to more modern firmware uP based counters without any disrespect to the programmers of more modern ones.


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 Post subject: Re: Frequency counter
PostPosted: May Mon 23, 2022 2:30 pm 
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Joined: Jan Tue 16, 2007 6:02 am
Posts: 5294
Location: Lexington, KY USA
When the detector of this receiver is oscillating, there will be a signal at the cathode of the tube that can drive a sensitive counter input. The counter input must be a fairly high impedance to avoid killing the regeneration.

The counter should be connected at all times to avoid shifting the received frequency when it is connected.

You could add a pushbutton to apply full plate voltage to the tube when you want to check the frequency, without disturbing the regen control setting.

There will probably still be a small frequency shift as the detector is moved in and out of oscillation.

One of the inexpensive China Post counter modules can be adapted by building a preamp to boost the signal from the detector. Probably some very careful shielding will be required to keep the counter's RF emissions from spoiling your reception.

Ted


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 Post subject: Re: Frequency counter
PostPosted: May Mon 23, 2022 3:31 pm 
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Joined: Jun Sun 15, 2014 4:37 pm
Posts: 2118
Location: Montreal, Quebec
Intersil specialized in "exotic" ICs. The 8038 function generator. The 7106/7107 DMM. Then tye frequency couter ICs.

Don't forget the 6100, a CMOS CPU that ran PDP/8 code.


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