I need some help - Antenna Warning on SWR Check
Discussion in 'CB Radio Forum' started by HD_Renegade, Jun 15, 2011.
Page 7 of 9
-
-
Trucking Jobs in 30 seconds
Every month 400 people find a job with the help of TruckersReport.
-
Recall that the VR6 adjustment only sets the threshold for that light. If your antenna system bad, then adjusting the threshold pot for the light is akin to putting a piece of black electrical tape over your oil pressure light (for folks who don't have an actual oil pressure meter).
As Bruck WA4GCH, putting a dummy load on the output of the radio is the best way to see if it's the radio or the antenna system that's "out of whack" (please excuse the technical jargon )
Even a properly tuned antenna mounted to a good RF ground plane and with good coax will make that light come on appropriately if some Golden Screwdriver has been in the radio to maximize the RF output on a feel-good meter, despite the amount of spurs and harmonic content in the signal. When that happens, the dummy load will accept it, cuz it's made to show a flat SWR across an enormous frequency range; but a properly tuned antenna will reject out-of-band signals, and especially 2nd harmonic energy (around 54 MHz) that the wattmeter is too dumb to show, but that the antenna isn't made to transmit. Such condition will reflect the out-of-band energy to the meter, and make the "Yo, something's wrong with your antenna" lamp, even though the antenna is working fine for its intended band.
Just a little sumpin' to keep in mind. I realized this is a necro-thread (someone revived it after a year of lying fallow) but since there were several posts since then, I thought I'd add a note -- cuz I have that kind of time )
73rabbiporkchop Thanks this. -
Thanks.
I got the PDF on here as you posted on page 5...
Dont send it. -
-
The PDF on page 5 worked for me! My SW was way high and after I did this is reading under 2.5 when it used to be at the max... I re calibrated after I did VR adjustment as well, super easy just make sure you've got small screw driver and be very gentle turning the VR
-
-
Has anyone had success with this fix on a cobra 29lx?
-
That's the way I adjust my 29's since thats what Cobra recommends as far as a way to adjust the lite without the proper load. The only thing that I do different, is when the lite first turns on, it is dim. So I keep adjusting VR6 slowly until the lite is bright. The reason is that without an antenna hooked up, the lite should be bright in my mind, instead of dim. I have used a 150 ohm load which should give an SWR reading of 3:1, but instead its sometimes closer to a 2:1 reading. Just goes to show that you shouldn't rely on the internal SWR meter in the radio, its not very accurate. Only use a good quality external SWR meter... usually at least in the $40 or more range. For example here is an old "new old stock" Lafayette meter.
LAFAYETTE SWR/ POWER METER 99-26395 ,NEW OLD STOCK
It's made out of metal and very good quality wise for $25 plus shipping. It's simple to use, you adjust the middle knob and watch the left meters needle till it's on the calibrate icon in the right upper corner of the meter, then you simply look at the right SWR meter and read its output. If the OP of this thread would have had an SWR meter years ago when he started this thread, it could have saved him a lot of time and frustration. But it still makes a good subject for people new to CB radio.rabbiporkchop Thanks this. -
-
Old thread, (I know) but I have a question about the procedure in that Doc. I realize it’s from the manufacturer and they would know their own product better than me, but I thought it was a bad thing to key a mic with no antenna connected? Their procedure specifically says to do just that.... if anyone reads this, could you please offer your opinion on this, maybe I am just misunderstanding something here.
Thanks in advance
Trucking Jobs in 30 seconds
Every month 400 people find a job with the help of TruckersReport.
Page 7 of 9