How to verify transmitter frequency??
 

Hi

Gave up on trying to get frequency with my digital counter.

Is there a different way ( without a spectrum analyzer) ????

How did they check TX freq in the 70s or the guys who built the heathkits ??

RE: How to verify transmitter frequency??
 

Know any ham operators? They might have one of those fancy scanners that you can program to listen to rc air band frequencies. Or maybe the local AMA folks might have a scanner they could let you use?

RE: How to verify transmitter frequency??
 

If it is an aircraft Tx you might want to check around to see if anyone has either a Polks Tracker Tx or a Multiplex Evo with the scanner.

Dan

RE: How to verify transmitter frequency??
 

To know exactly the frequency your transmitter is on you must stop the modulation. If it is a AM transmitter you can then use your counter to measure the carrier frequency. If it is a FM transmitter you will get a number that could be off by the amount that the manufacturer shifts the frequency either up or down or you could get the main frequency. All this requires that you do some work on the transmitter. I am the Frequency cordinator for your district and I have the AMA Receiver that you can borrow. However it is just a short wave receiver and is not very accurate as far as frequency is concerned. I also have a Tracker transmitter and it will not give an accurate reading It is very broad in it's receiving ability. If there is someone on the next channel the tracker will refuse to turn on and give you it's warning signal. As a starting point if you have a transmitter that has a module to change channels you can find the modulation wire On my JR there is a small connector with three wires one is black one is red and one is white Guess which one is the modulation???? If you have a scope you can see the modulation on this wire To stop it you must figure out the circuit so you do not blow something Sometimes you can just disconnect the wire but my advice stops here.

RE: How to verify transmitter frequency??
 

Hi Al,
I recently bought a Yaesu VX7R, does a pretty good job of finding the frequency.
Its narrow enough (12 kHz/25kHz (-6dB/-60dB)) to keep to a single RC channel.
Also has a spectrum analyzer that scans +/- several channels (5,8,14,29,or 60 channels) and the channel step is selectable as well (5/9/10/12.5/15/20/25/50/100 kHz ).

And is works as a regular scanner so I have 2 memory groups to scan 50MHZ and 72MHz bands. Guess I'll have to add 53MHz just for you.

Will be glad to show it to you next time I see you at the field.

Larry Gaalaas

RE: How to verify transmitter frequency??
 

The RF section was completed and verified by Heathkit and supplied in the kit as a complete unit.
The frequency was verified in the 70's the same way they do it today. With a frequency counter.
If you can't get it to work find someone with electronic test background and let him do it. I am sure he will be able to make it work.

RE: How to verify transmitter frequency??
 

Depending on brand and other factors, what you see may be different from one transmitter to another. If the radio is newer, your best bet is send it back to the guys who made it. If not, you must find a tech who knows what the particular manufacturer's tuning requiremants are and how to test them with the proper equipment. There are ways radiomen can test and tune for frequncy and output, but they require us to know tricks and build our own little test fixtures and boxes.

Any good tech will probably have a Spectrum analyzer (as I do). A spectrum analyzer may seen very expensive to average person, but to a radio man it is nearly as valuable as a screwdriver.
With it, I can test output and tuning at the same time.

If your radio is older and can't be checked out by the makers, you might try Tony Stillman at Radio South.