Frequency Counter Question

[Raccoon]

I've been looking at frequency counters online, and I've noticed that a lot of them don't have their BNC alligator clip test leads ... and I was wondering, if I buy a replacement test lead for whatever frequency counter I buy , will any BNC test lead work, or will I only be able to use brands specific to that frequency counter ?

Like Heathkit only for a Heathkit ? ... and so on .

 

[Captain Kilowatt]

Any of them will work, including homemade cable assemblies. Been there, done that.

 

[Raccoon]

Any of them will work, including homemade cable assemblies. Been there, done that.

That's what I figured, but I thought I'd ask first just to make sure .
Thanks Captain Kilowatt .

 

[brandon7861]

The brand don't matter, but trying to align a radio with an alligator type test lead on your frequency counter might not go as planned. They don't come with them because they would only work for audio and low impedance test points. Most radio oscillators will go way off frequency or die completely with those types of cables connected.

 

[Pez]

The brand don't matter, but trying to align a radio with an alligator type test lead on your frequency counter might not go as planned. They don't come with them because they would only work for audio and low impedance test points. Most radio oscillators will go way off frequency or die completely with those types of cables connected.

Exactly this. A few FC tips:

You can often get by with adding a coupling capacitor, like a 100pf on the end of your random cliplead to reduce the loading on the circuit you are measuring. It still will load the circuit you are measuring, but not as much and might get you out of trouble.

You will also run into issues where the signals you are looking for, are too small for the FC to see. You can sometimes get around this by using a cheap broadband amplifier to boost these signals before they enter the FC (put it between your probe, and the FC). Like this one: https://www.amazon.com/dp/B08THYZWNQ?tag=worradfor-20

Some extra advice: if you can afford too, spend the extra on a FC that supports a 10MHz external reference input. It is absolutely worth it IMHO.

73

 

[Smokinone]

I generally use an oscilloscope probe with my Counter. Probe Master makes nice ones, in the USA, and after buying several chineseiam brands, I have found they are worth the added cost.

 

[tramd]

Also, a sniffer probe is a good thing to have. It can be used to read a signal without direct contact. A direct connection can sometimes pull the signal down a bit and give you an incorrect frequency reading. If the sniffer probe it is insulated, you won't have to worry about touching something that could cause a short or damage your counter. You can make your own sniffer from a piece of coax. I'm sure there are videos on how to do this. A DC blocker attached to your counter is another item I would recommend if you use a direct connection type probe or clip. It will prevent damage to the counter if you touch a high voltage DC point with a regular probe or clip. They can be used with your other test equipment also, especially if you have a spectrum analyzer. It will protect your equipment and is better than always having to remember to attach a cap to your probes or clips.

 

[brandon7861]

Also, a sniffer probe is a good thing to have. It can be used to read a signal without direct contact. A direct connection can sometimes pull the signal down a bit and give you an incorrect frequency reading. If the sniffer probe it is insulated, you won't have to worry about touching something that could cause a short or damage your counter. You can make your own sniffer from a piece of coax. I'm sure there are videos on how to do this. A DC blocker attached to your counter is another item I would recommend if you use a direct connection type probe or clip. It will prevent damage to the counter if you touch a high voltage DC point with a regular probe or clip. They can be used with your other test equipment also, especially if you have a spectrum analyzer. It will protect your equipment and is better than always having to remember to attach a cap to your probes or clips.

There may be an issue with coax sniffer probes (H-field probes) in that that they are made of 50Ω coax and the tiny current they pick up produces tiny voltages a FC will not see and is likely only going to work with something like a spectrum analyzer with a very sensitive front end. Most FC's require tens to hundreds of mV to lock on and count. To get voltage like that out of an H-field probe, you will need an amplifier with 50Ω input. 6-36MHz will couple well into an H-field probe, but the oscillators are still only running at 1mA or so and the voltage produced inside it will be from only a fraction of that. Since oscillators, even at low currents, produce large voltages, the high impedance E-field probe is preferable.

I have a coax sniffer probe made of 1 foot of coax with about a 3/4" pickup loop. With it connected directly to my scope set to FFT (no 50Ω terminator) with the probe next to the 7.8MHz oscillator in my washington, I pick up the oscillator at about -60dBm. Thats only 225uV! A FC is not seeing a 225uV signal. Another issue is that H-field probes work better as frequency goes up, so that weak signal you are next to will be swamped with other signals too, like pre-filter harmonics. It is absolutely useless for FC work IMO.

 

[Pez]

Also, a sniffer probe is a good thing to have. It can be used to read a signal without direct contact. A direct connection can sometimes pull the signal down a bit and give you an incorrect frequency reading. If the sniffer probe it is insulated, you won't have to worry about touching something that could cause a short or damage your counter. You can make your own sniffer from a piece of coax. I'm sure there are videos on how to do this. A DC blocker attached to your counter is another item I would recommend if you use a direct connection type probe or clip. It will prevent damage to the counter if you touch a high voltage DC point with a regular probe or clip. They can be used with your other test equipment also, especially if you have a spectrum analyzer. It will protect your equipment and is better than always having to remember to attach a cap to your probes or clips.

I have this cheap set and they are really good. It even came in a nice little box. You can make your own, but this is great value for money IMO.

https://www.aliexpress.com/item/1005005335886552.html