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Message |
    
Crackerjack
Advanced Member
Username: Crackerjack
Post Number: 595
Registered: 7-2004
| | Posted on Friday, June 03, 2005 - 2:13 pm: | 
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Tech808 and others here have frequency counters hooked to the output/input of their systems.
I am wondering how you guys use them to measure the frequency of a SSB signal, seeing as there are no stable carrier freqs to sample?
How can you tell, for example if a received signal is off frequency? |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 342
Registered: 6-2004
| | Posted on Friday, June 03, 2005 - 5:58 pm: |
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If the counter reads from the radio's oscillator rather than the RF output it doesn't matter what mode you're in. Of course it'll also read the SSB shift too, so it's nice to have a counter that takes that into account.
For receiving you adjust the clarifier until the pitch of the signal is correct and that'll tell you the frequency of the received signal.
CB counters have a resolution of 100Hz (4 decimal places) or 1000Hz (3 decimal places) and both are pretty coarse for SSB. A frequency difference of as little as 10 Hz can be noticed by an experienced ear when chatting with a familiar voice.
Don't forget that the counter's own oscillator drifts a bit so the margin of error can be even larger. So essentially they are just channel displays and shouldn't be considered highly accurate. |
Crackerjack
Advanced Member
Username: Crackerjack
Post Number: 601
Registered: 7-2004
| | Posted on Friday, June 03, 2005 - 7:25 pm: |
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I'm talking about the counters like Lon uses that are part of the DOSY meter, the ones that are reading RF off the Coax. |
Nobodyknows
New member
Username: Nobodyknows
Post Number: 8
Registered: 4-2005
| | Posted on Friday, June 03, 2005 - 8:08 pm: |
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The way I use my inline freq counter to dial myself in on SSB is to go to the AM side and key up and dial the freq in. Then on SSB it's pretty darn close to being perfect. Using that method works well for me and this radio im using. No one has ever told me i was off freq.
Using a 148GTL-DX
To know how far off frequency someone else is talking is hard to know without a freq counter that tracks your tx and rx. Export radios with the freq display come in handy if you're looking for a spot on match, or the type of external counter that you have to connect to the radios circuit board. |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 343
Registered: 6-2004
| | Posted on Friday, June 03, 2005 - 8:52 pm: |
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Inline counters are pretty much for AM, FM or CW - signals with carriers. You can switch to AM to check quickly, but you'd have to do that each and every time you change frequencies.
About the only way to directly read the frequency of a SSB signal with an inline counter is to feed a known frequency tone into the microphone input and then read the output signal with the counter. Of course then you're adding another variable of the tone's frequency. So then you have the three variables of the radio's oscillator, the frequency counter's oscillator, and the tone generator's oscillator. You can't really expect much accuracy.
The best way to tell if you're on frequency is to listen to others on the frequency because that's ultimately what matters for communication.
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Crackerjack
Advanced Member
Username: Crackerjack
Post Number: 602
Registered: 7-2004
| | Posted on Friday, June 03, 2005 - 10:04 pm: |
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I thought so. So basically when I haar some one tell another guy he is off freq, it is purely his opinion.
I was listening to one guy the other night, because he had a freq counter, telling almost every other user on the channel -how far off freq they were.
To me, he is the only one that required me to tune in on him. It seems that all the others were of freq, at the same amount. I guess? LOL
Thanks.. |
Nobodyknows
Junior Member
Username: Nobodyknows
Post Number: 11
Registered: 4-2005
| | Posted on Friday, June 03, 2005 - 10:36 pm: |
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There are some snobs like that, I ignore the snobs that can only talk about how great their radio is and how bad everyone elses is. If you're close to frequency and in there with everyone else, Thats good enough for me. |
Yankee
Advanced Member
Username: Yankee
Post Number: 632
Registered: 7-2003
| | Posted on Friday, June 03, 2005 - 11:14 pm: |
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Hi Dave, Welcome to the forum and CEF radio club, I'm Carl down here in Purcell and I must hear the same person you do telling others that there off frequency, and how great his radio is.
Carl CEF-357 |
Oldpirate
Member
Username: Oldpirate
Post Number: 59
Registered: 11-2003
| | Posted on Saturday, June 04, 2005 - 2:49 am: |
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Crackerjack, what you do is tell them that according to your Icom, Kenwood or Yaesu it's them that's off frequency and get some of your buddies to back you up. That usually shuts them up straight away. |
Vanillagorilla
Member
Username: Vanillagorilla
Post Number: 53
Registered: 4-2005
| | Posted on Saturday, June 04, 2005 - 10:42 am: |
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I borrowed a very cool portable freq counter from a friend to help me work on something. Its a radio shack model that you simply place next to your transmitter and turn it on. Takes a few AA batteries and has its own antenna to pick up the freq. Will find from 0 mHz all the way through 1.3G and everything in between. EASY way to see your freq as soon as you key up. Also has 50ohm to HiZ impedance...cool tool!
Cat# 22-306
Hank '905 |
2600
Advanced Member
Username: 2600
Post Number: 568
Registered: 7-2002
| | Posted on Saturday, June 04, 2005 - 11:47 am: |
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For an AM transmitter, all you do is turn up the carrier, and turn down the mike gain. For a SSB transmitter the carrier was removed inside the radio, and nothing comes out until you modulate the transmitter. Even on AM, the reading on an external counter will bounce randomly when you modulate the AM carrier.
The only way to get a steady carrier (that you CAN count) out of a SSB transmitter is to modulate it with a pure audio tone into the mike.
We use a home-brew 1 kHz tone generator with a speaker on one side. With the mike face down on it, a SSB radio will deliver a carrier that can be read on an external counter.
A whistle will do the same thing, but only if you have perfect pitch. So long as your tone frequency is precise, this method works. The one we use is crystal controlled, within 1 Hz.
With a tone pitch of exactly 1 kHz, the counter reading will be exactly 1 kHz below the (internal) carrier frequency on LSB, and 1 kHz above on USB.
This method requires you to add/subtract 1 kHz from the counter reading, but it's the only method I know.
On AM, folks argue endlessly about whose modulation sounds bad. On SSB, the all-time favorite argument is about who's off frequency. Seems like the guy who gripes the most about other folks being "off frequency" hasn't calibrated his frequency display in 5 years or more. Who cares what frequency you're on so long as it's the SAME one as the other folks on the channel?
73
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Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 346
Registered: 6-2004
| | Posted on Saturday, June 04, 2005 - 3:36 pm: |
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Crackerjack - Depending on what kind of radio the person is using he very well could know how far off frequency people are, but not by using a CB frequency counter.
Most HF rigs have a procedure in their manuals to "synchronize the display" so they are on frequency. It involves tuning the radio to the 10 MHz WWV broadcast and adjusting the master oscillator of the radio until the radio zero beats with the WWV broadcast. The WWV broadcast is used as a frequency standard all over the world because of the very tight tolerance used in the maintenance of the transmitter. When I sync my TS450 to WWV I can be sure that I'm dead on frequency and I can check it regularly by tuning back to 10 MHz. When I touch up the frequency of my SSB CBs I zero beat them to my TS450 and I can get them to +/_ 10Hz.
If someone wants to know how far off frequency they are I can listen to them on my TS450 and tell them within 10Hz.
I've run into folks who have told me I'm off frequency too. When I ask them how they know they usually tell me about their radio with a built in counter. After I explain how I adjust the frequency of my radios I usually don't hear about it anymore. |
Kilowatt
Intermediate Member
Username: Kilowatt
Post Number: 208
Registered: 2-2004
| | Posted on Monday, June 06, 2005 - 9:40 am: |
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Man, I love WWV, too. I do wish that they would start transmitting on 25.000 Mc again, though. Then folks would have an easy way to calibrate all of those multi-channel exports! |
Bruce
Senior Member
Username: Bruce
Post Number: 2818
Registered: 9-2003
| | Posted on Tuesday, June 07, 2005 - 7:18 am: |
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WWV is a good way to check frequency back many years ago we used crystal cal boxes to set the dial on the radio you zero it to WWV and you had neat 1 meg, 100khz or even 10 khz markers.
My FT-620 has one built in and a small cal knob for the dial! |
Bruce
Senior Member
Username: Bruce
Post Number: 2819
Registered: 9-2003
| | Posted on Tuesday, June 07, 2005 - 8:16 am: |
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Here is a simple one
http://www.rason.org/Projects/calibrat/calibrat.htm |
Crackerjack
Advanced Member
Username: Crackerjack
Post Number: 636
Registered: 7-2004
| | Posted on Tuesday, June 07, 2005 - 8:39 am: |
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When did Ft. Collins quit trnsmitting on 25,000KHZ?
That explains why I can't raise the signal. I used to be able to pick up a harmonic on 30,000KHZ as well. |
