The AM Forum

I have a very nice Valiant here and I am wondering how to measure the tx frequency when using the VFO. Say I want to set up on 7.255 MHz (freq chosen at random) how do I know when the VFO is at that freq.

If the answer is a frequency meter would you kind enough to recommend a make and model.

Thank You, and sorry for the newbie question.

I use whatever receiver I have paired with the transmitter and adjust the VFO so the spotting signal is heard in the receiver.  Otherwise you can use a frequency counter or my favorite answer, a low cost digital readout portable shortwave receiver.  I would be lost without my multipurpose Grundig YB-400 :)

You're allowed only one newbie question per month. ;D

A frequency counter would be the best way to find your transmit freq.  If the transmitter has a spot-frequency button you can zero beat another signal from someone in the QSO that can tell you what frequency they're on.

Fred

 "  You're allowed only one newbie question per month. ;D  "

Yeahbut,  here, we have newbie rollover questions.......   he's been a member since Sep., so he has a few questions that rolled over.  Check his postings.


klc

You're allowed only one newbie question per month.  ;D



Man  am I overdrawn.............

Rich

Here's der wrench in der works. It's possible that your VFO set on 7.255 is putting out half of that frequency as most old school VFO's that I've seen double in the transmitter to get on that frequency. Again you would be looking for half that freq on a your freq counter if you are just measuring the VFO alone. It may even double from 160 meters to get on 75 meters.

I use a Frequency counter. It is an old Fluke (forget the model) with an LED display. It had a 10Mhz crystal timebase, but that timebase drifted a few hundred hertz during warmup. Today we can get temperature compensated crystal oscillators cheap where 10Mhz is a common frequency. My point is an old counter can easily be updated with a surplus precision timebase. Use WWV at 10.00 Mhz to calibrate your timebase.

You can hook the freq counter to your rig to your transmission line with an RF tap (Byrd makes them), or a voltage divider. The idea is to drop the level to ~ 0dbm to the counter input. I like to have a coax switch to tune my rigs into a dummy load. While on the dummy load, I set the frequency to whatever I want, and then I'm within 10 hz since my timebase drift is now minimal.

If you have a lot of RF in the shack, maybe just connect a 2m rubber duckie into the counter. That won't work with the dummy load however.

Keeping the Valiant within 1 Khz of setting will be a challenge however unless the rig is already warmed up....

Jim
WD5JKO

I use a cheap freq counter...

as you can see in the first page of my blog... it works great

http://boatanchors.tumblr.com/

AADE (Almost All Digital Electronics) has kits and assembled units that will allow for offsets, doubled frequencies, etc. in the vfo.  They even have programmable counters for your receiver so it will read out in TRUE rx frequency, taking IF offsets into account. 

I have their LC meter.  GREAT products, great service.  HIGHLY recommended by me.

Get one of these on your receiver, and then use the SPOT feature.  OR, get one for your rx AND your TX...  Or, just get the bench counter (as I did), and use a tap to read your TX freq directly on CW or AM carrier.



--Shane
KD6VXI

Freq counter off of ebay.  I paid less than $25 for mine. Works FB.  Not lab quality but jives with the display on my R390A or close enough.

I have about 5 freq counters including some HP lab grade 10 digit counters.  I used them to calibrate at $40 para Dynamics PDC356 and run that off a wall wart power supply.  I jamed a wire into the signal port on the Freq counter and ran that over the back of the table. It picks up anything I transmit on in the shack including my 2 meter stuff. I have had this thing for 6 or 7 years and its DEAD on acurate.

C

Yes I can see, too bad I can't understand!  It's not fair us Americans are not taught to be fluent in other languages the way other countries are.
BTW- Really nice blog and great videos...that freq counter works perfect with that ART-13

http://66.163.168.225/babelfish/translate_url_content?.intl=us&lp=it_en&trurl=http%3A%2F%2Fboatanchors.tumblr.com%2F

very excellent!

I've faced the same counting issue, perhaps slightly more complicated, on the Collins 618S-1 tranceiver. This uses a crystal bank but can be modded to use a VFO from the later SSB version of the set. I have three of the sets. Sadly they just sit and stare at me. It is BTW a super SWL machine.

The set has 4 bands and multiplies the crystal by 1,2,3 or 4. While it would not be a big problem to hack an old frequency counter to let the gate run 1,2,3 or 4 times the normal time, there is a 250KC offset on TX due to the I.F, and this number, regardless of the band, has to be added to the count. It has to be either loaded into the counter or appended to the count after.

There are a few kits and appliances for this sort of thing created in the last 10 years, but I didn't want an LCD, at least give me LED digits. It's also a case of this need going back 25+ years, so while I put it off for 2 decades due to no time to do it, add-on appliances have become available.

All things come to he who procrastinates.

Nice job on the video, it's fun to watch the ART-13 tune like that!...

Direct link to the ART-13 video...

http://www.youtube.com/watch?v=0KnZ52cNM8U&feature=player_embedded