Ok, for you radio guys, if I tune the antenna with the meter, and then remove the meter, how much does that change the SWR?


One of the reasons I'm buying the meter that I am, is because it's a little higher quality, although I don't know if it can stand up to the vibrations on a Harley.

 

How much it changes the SWR is influenced by several factors specific to your particular situation.

You said you planned to use a 3 foot jumper. The longer the jumper, the less accurate the meter reading is as compared to what the radio sees. A general rule of thumb is anything 10% of operating wavelength will adversely affect SWR. 11 Meters (CB band) is 36 feet. 3 foot jumper is approaching that 10% rule.

I would suggest a 1 foot jumper for the measurement, then remove the jumper & meter when done matching. I have never left an external SWR meter installed in line after completing measurements.

I do have an automatic antenna tuner (with built-in SWR meter) installed permanently in my G5RV amatuer radio fixed station, but it's because that antenna works on multiple bands, but needs a tuning circuit to impedance match to the radio/amplifier. I do not use the tuner when using a resonant antenna for a specific band. (comments in this paragraph are unrelated to the issue, but added to illustrate a specific example when leaving the SWR in the antenna would be appropriate)

 

Makes sense to me, great advice as usual!


I'll get a 1' jumper and remove the meter after tuning.


Thanks!

 

You will also want the CB SWR adapter kit, p/n HD-48037. This allows the SWR meter's SO-239 connectors to be adapted to the HD wiring connectors.

 

Even if I hook it up at the module inside the fairing?

 

That's where the adapters are used.

 

the radio has a female TNC, therefore its cable will be a TNC male. Your meter will have 2 of the (female) S0-239's

 

Having a meter in the radio is altogether different than having one in line. The fewer connections you have between the radio and the antenna the less loss. The circuity added inside a standard SWR bridge/meter is definitely not needed in the transmission line permanently. You also have two additional connectors and the likely hood of a bad connection at some point isn't worth any thing that you may think you gain from having the SWR bridge in line. The SWR meter is only a measurement device to tell you what your SWR is. It does nothing to improve the SWR match. If you have a 3 to 1 match you have lost 25% of your output. 2 to 1 is 11% and 1 to 1 is 0% loss. The only possible reason I could see for leaving an SWR meter inline under a cowling is so the store could sell more. The likely hood of the CB surviving a bad connection or open connection is slim also.

 

I ordered a TNC to ISO259 connector to put directly into the radio. I have an 18 foot length of coax with 2 factory PL259 connectors. I plan to connect one end of the 18 foot coax to the radio and route it to the tour pack. I plan to cut the coax and put another PL 259 in the same spot behind the seat and use a Double female connector connecting the remainder of the 18 feet of coax there and on to the antenna. The remainder of th 18 foot will be tied in a figure8 configuration in the tour pack under the liner. The swr can be checked at the double female connector with no jumper so when the meter is disconnected there will be no change. Better shielded coax at the right length (18') with some grounding straps should make the radio perform as well as a 3 watt radio can. My ham call is KG4PUF

 

Sounds good. I don't know if I would get too hung up on that 18' of coax. Don't forget the Velocity Factor in the calculation. With RG58 11'8" is 1/2 wave and 8X would be 13' 5". Personally I wouldn't worry about either one as much as I would rolling the coax up even in a figure 8 and putting it on the ground plane of aluminum in the bottom of the tourpak. I suspect you will find the antenna is not tune able the way it is. My 10 limited wouldn't work with the factory fiberglass and I put a set of metal whips from an 08 and it worked good after that. At least you are doing something instead of talking about it like I am.