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 Post subject: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 1:09 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 162
There are already a good many threads and posts out there concerning the el-cheapo Chinese frequency counters in the $4-15.00 range and I have reaserched them looking for a clear definitive yes or no answer to a simple question. Can you set one of them on top of a signal generator, like a Heathkit Model RF-1 and use it to keep an eye on the dial acuracy? What I mean is, can you just get a reading through the air with no wires? Thank you.

PS If anybody cares to point out one of the many cheap Chinese counters to do this with I'd be appreciative.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 1:20 am 
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Location: Mpls, Minnesota
Most of those cheap ones won't even pick up the signal when you connect it to the generator.

Dave


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 1:37 am 
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Location: Seattle WA US
A signal generator that leaks so much RF that you can get reliable frequency measurements out of the air......isnt worth spending your time on. You should plan on delivering at least 100mv of RF, interference free, to your counter if you expect an accurate frequency measurement. For expensive or good cheap counters.

-Chuck K7MCG


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 1:40 am 
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Location: Simonton, Texas
I bought a couple of those cheap chinese counters last year they were labeled PLJ-6 led.

I use them for a digital readout on analog dial receivers. They can be programed for an offset

frequency reading. I just checked on with my signal generator and it is stable with a -14 dbm signal.

That is about .045 volt.I hope this helps.

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 2:09 am 
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I would suggest simply getting a brand name moderately priced digital readout radio; Kaito, Radio Shack, etc. I use a Rat Shack DX-395 that I bought on eBay for about 15 bucks, that many years ago, to verify frequencies on analog sets. If I tune it to 910 kilocycles, it'll pickup the second harmonic of the generator when set to 455 KC, with the generator's hot lead set on top of the radio.

I also have a Sony ICF-2010 which tunes down into long wave, and can directly pickup 455 KC as well.

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 4:29 am 
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I bought a four or five of them and the sensitivity was about the same as what Koby mentioned, 50mV.

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 4:58 am 
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Mikeinkcmo wrote:
I bought a four or five of them and the sensitivity was about the same as what Koby mentioned, 50mV.

Thanks everybody. So in the literature the Heathkit RF-1 max output is 100,000 microvolts which converts to 100 millivolts, so ideally it should work when physically hooked up to the cheap counter. Not exactly how I wanted, but at least a chance of having better accuracy than just using the dial.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 12:13 pm 
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Don't know about your generator model in particular, but the vast majority of those kit type generators have very distorted output wave forms full of harmonic content. That was how they were able to get output on the higher bands.

That translates into its most likely going to be difficult to get accurate readings.

When you do want to check frequency, make sure the modulation is "OFF".

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Dec Sun 02, 2018 3:28 pm 
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Joined: Jan Mon 28, 2013 9:35 pm
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Location: Santa Rosa, CA
I've also bought and used a number of these Chinese counters
and found them to be as sensitive as other have mentioned.
Very flexable (with programmed offset) and reasonably accurate.

My suggestion would be to find a spot in your sig gen before
the output attenuator and couple the counter in there.
It can be as simple as wrapping a wire around the plate
lead of the oscillator tube one or two turns. I would NOT
connect the input of the counter directly to the output
of the sig gen.
Steve

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sat 16, 2019 11:34 pm 
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As an update to this thread I started, I'm fixing to get on my second alignment job with my little Mercury 1500 signal generator and cheap Chinese frequency counter combo. While I got through my first alignment, it was a fight the wole time to get the counter to give a true reading. I had been alligator-clipping on insulated wires to avoid hooking the signal generator DIRECTLY to the frequency counter positive. I fought the signal generator attenuation control constantly trying to find balance between a high enough output for the LED display stability, versus overloading the receiver I was working on. Further the higher in frequency I went, it became nearly impossible to get a good reading.
I just decided to connect the signal generator directly to the frequency counter through a .022 cap I had as a stray on the work table. Voila--a stable display at any level. I was told not to hook the 2 together, but it doesn't SEEM to be hurting the counter, unless someone here know something I don't. Thank you.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sat 16, 2019 11:47 pm 
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You did what used to be called a "dummy antenna", by connecting the generator -through a small value cap- directly to a radio (in your case, the counter). No, you won't hurt anything with this setup.

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sun 17, 2019 12:03 am 
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Joined: Jan Thu 24, 2019 1:22 pm
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Location: Centennial, Colorado 80122
If you install a external connector connected through a small capacitor in front of the attenuator like the BK 2005A does I would expect it to work ok.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sun 17, 2019 12:23 am 
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Bill Eccher wrote:
If you install a external connector connected through a small capacitor in front of the attenuator like the BK 2005A does I would expect it to work ok.

I hate to sound ignarant since I just passed my Technician and General Class tests this morning. But where on this schematic would you recomment this tie-in be? Also, since I have a stash of caps of all kinds, would the .022 be good enough?


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Mercury1500 schematic.jpg
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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sun 17, 2019 12:42 am 
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Connect the cap to the output line on the right. The cap value isn't critical; .022 is fine.

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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sun 17, 2019 1:03 am 
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Joined: Jan Thu 24, 2019 1:22 pm
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Location: Centennial, Colorado 80122
It needs to go to the top of the pot or pin 8 of the 12AU7 so the atten does not effect it.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sun 17, 2019 1:05 am 
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Location: Mpls, Minnesota
Pin 8 of the 12AU7

Dave


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Sun 17, 2019 1:19 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 162
Thanks. Pin 8 is what I thought. If you saw this little Mercury you'd see that servicing it take an inordinate amount of disassembly and detachment of wires, for such a simple little instrument. Lately I've had pretty good luck with simply removing a tube and winding a couple loops of stripped telephone wire around the needed tube pin and plucking it back in as a take-off point. Kind of lazy and unprofessional, but it's not destructive and works.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Mon 18, 2019 12:02 am 
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Now I have a very important question. As you can see I've gotten the counter installed, tapping off where the plate of the tube is connected to the pot. I tapped off with a .022 cap. Im very happy with the results. Now the counter holds a steady reading all the way down to minimum output. This is a new generator to me and I have a question. If I send a signal to my Hammarlund HQ-100 set at 1110 WBT radio in Charlotte (or any other known accurate place on the dial), this generator will peak on my S meter right where the frequency counter says. This happens both modulated and unmodulated signals. But with a modulated signal, the tone isn't particularly loud, but it does have a pretty decent sine-wave quality, and the VU meter IS peaked. But when I detune the radio below signal, I lose my S meter peak (as expected), but the 400hz to gets much louder and sounds square-wavish. In other words, if I were to align a radio with a modulated tone using a meter connected to the speaker, I would have a mis-aligned radio (logically). Why is the modulated tone not loudest at the same frequency that peaks the S meter?

Edit: The signal gerator was this way before and after I did the instalation of the counter.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Mon 18, 2019 5:10 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 162
I think I figured out the answer to my own question in the above post. This signal generator seems to have a fairly strong output even when the attenuator control is at the the minimum. Otherwise I risk getting an image signal very close to the correct one. Referring to the loud 400hz distorted tone, it disappears if I keep the output low. It gets loud pretty quickly as I turn up the output. And it is too close for comfort to the desired frequency. A mistake can easily be made if you are aligning your radio by hooking a meter across the speaker. Since the Carrier Level meter on this Hammarlund takes its signal from the AGC line, perhaps that might be a better place to attach the VTVM on alignments on simple 5 tube consumer radios too, rather than the common alignment instructions that say hook up to the speaker? One thing is for sure. now that I've done enough experimentation to actually trust this Chinese cheap counter, Ive gotten a whole new appreciation for how easy it can be to misalign a radio by mistaking the actual correct frequency of your generator.


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 Post subject: Re: Question: Cheap Chinese Frequency Counters
PostPosted: Feb Tue 19, 2019 1:25 am 
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Location: Arizona
The real cheap Chines kits for <$4 https://www.ebay.com/itm/DIY-Digital-LED-1Hz-50MHz-Crystal-Oscillator-Frequency-Counter-Meter-Tester-Kit/263936482470?epid=509681213&hash=item3d73d71ca6:g:09AAAOSwf8Fbm4PG:rk:2:pf:0 don't have any input signal amplifier so they need at least 2.5V P.P input to measure any signal.


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