Does anyone know wny I cant use a digital frequency counter to check a tube signal generator. I have 3 signal generators in top conditon, one is an EICO 625, and for some reason, the freq. counter will not read above 430KC. below that (1st band) it works great. I have tried coupling caps on the output and have played with the RF modulation with no results. Is it time for a digital signal generator?

If your signal generator is Digital or "tube"-analog has NO bearing whatsoever on the actual output sigal.

The output signal is either there or not there.

The signal output level must however be sufficient for the input threshold level of your frequency counter.

You signal generator should be able to read the signal thogh unless your generator's output is extremely low do to some failure.
The important thig is that you must NOT be modulating the signal generator with augio at the time of your reading as the that can confuse your signal generator.

There should be a 400hz or 1000hz audio modulation on/of switch somewhere on the generator.

You should have it OFF when you read the signal gen's output with the Freq counter. Them you can turn it to the freq you like such as 455khz.

Then later when you couple the signal generator's output to the radio ....THEN you can turn the audio modulator on.

The audio modulation was off on all three of my different signal generators yet the results were the same: Only reading between 115KC and 431KC. Too much of a coincidence for the problem to be the signal generator. My guess is that the RF is too 'dirty' for the digital meter to lock on.

What type or brand is the freq meter?
What are the specs of your digital freq meter?
What is the input voltage threshold? And is the generator capable of putting out enough voltage to meet that threshold at the higher frequencies? My guess is that most generators probably do.
Then maybe it's the fault of the freq counter. Is it part of a handheld mutimeter? Maybe that's a concern. Do you have access to another known good freq meter to compare with?

I just tested my cheapo handheld multimeter...
Supposed to have a freq reading range of 10hz to 10mhz
Doesn't say threshold levels.
Anyway it seems it can read the low frequencies like 60hz by just being close to the AC line. I can also read the audio out from my Heathkit model 1G-102 sig gen. because that puts out mucho volts (AC)... like 50v pp AC as seen on my o'scope. And the meter reads it all the way down to about a few volts.
But it doesn't read a thing on the RF side that seems to only put out about 500mv pp.
I don't have the sig gen specs to see if the RF level is below spec... but I do know using it everday that it's always plenty for my radios.

:What type or brand is the freq meter? Fluke multimeter

:What are the specs of your digital freq meter? Do not know the specs.

Are you saying that you cant get a reading on the RF side of your signal generator either? I will measure the output of my generator tonight. The strange thing is that my counter will go up to the top of the first band (431kc) yet when I switch to the second band, 431kc+, the counter goes to 000. You mention voltage on the higher freq's but I would think going from 431kc to 455kc should not be that big of deal.

Do you think a Function generator has enough output to tune IF's in a radio?

I use a DIGITAL radio to test my TUBE signal generator with fine results. I just tune in the signal and find out where it's actually falling. My generator is almost never right on, probably because it's a cheapie. Keep in mind that most signal generators put out a rather broad signal, at least 10KC in width. The signal they put out, like any signal, has a peak, and this is what you tune your radio to. Your frequency counter might have trouble with the broad range. Also, many signal generators do not have filters, and so they put out harmonics. Actually, the highest band on my signal generator has no switch position. All I do is use the harmonics of the next lower band. Strange, but it works, and saves a switch position as well as other things. Actually, the next lower band uses straight wires for coils, since the frequencies are already so high, and the thing uses the kind of tuning condenser that you'd use in an AM radio's oscillator section, so I don't know what on earth you'd use for a coil if you actually wanted a higher band. When most of us tune up a radio, especially in the short wave band, whe have to look out for harmonics, so I wouldn't be surprised if your frequency counter is picking up these harmonics and is getting confused. The only way to eliminate the harmonics would be to either have multiple stages in the generator (added expense), and/or multiple tuned wave traps (another added expense, and having all of these stay synchronized throughout their range would be a fine trick to do).

Thomas