Antenna affecting power output

[dugcyn]

Most likely a stupid question but hey I am just a machinist in trade.

I have a radio in truck that in testing with a sure com puts out at high power setting 10 watts. it is rated 50 watts. when I hook this same radio to base antenna sure com reads 17 watts. what say you.

any input would be appreciated, i love learning new things. Radio is not my end game but a tool and would love to learn how to use it best.

fyi same radio, very similar input power supply, same frequency (gmrs).

[gortex2]

what antenna on truck ? 

[Sshannon]

1 hour ago, dugcyn said:

Most likely a stupid question but hey I am just a machinist in trade.

I have a radio in truck that in testing with a sure com puts out at high power setting 10 watts. it is rated 50 watts. when I hook this same radio to base antenna sure com reads 17 watts. what say you.

any input would be appreciated, i love learning new things. Radio is not my end game but a tool and would love to learn how to use it best.

fyi same radio, very similar input power supply, same frequency (gmrs).

What does the Surecom say is your reflected power?  What does it say is the SWR?  Where is the Surecom in the transmission line (coax), at the antenna or next to the radio? What kind of coax are you using?

Welcome to the forums!!

[WRQC527]

1 hour ago, dugcyn said:

Most likely a stupid question but hey I am just a machinist in trade.

No such thing as a stupid question. And being a machinist, you're probably smarter than half the people here. Describe for us, if you will, your setup. Radio make and model, antenna make and model, how it's all mounted, wired, that kind of thing. More info from you = better answers from MyGMRS. 

[dugcyn]

thanx

trying to keep brand out 

antenna in truck is quad band and antenna at shop is ??? looks has 5 spikes 2 near vertical. I do have a comet 70' and last tested this radeo put out 46 watts. have not gone back there yet, was new when i got that result.

the ??? antenna works perfect with other radios 70cm and 2m. reads 1.03 swr.   fwy my truck antenna is at 1.9 swr.

not sure of wire to truck radio but base is setup with lmr400  and done correctly.

could i be loosing that much in cabling or antenna. what is this telling me. no worries am talking on radio just fine but trying to learn how to make this a lean system.

thanks all

[WRQC527]

2 hours ago, dugcyn said:

trying to keep brand out 

No reason to keep the brand out. 

Also, if you are using a quad-band ham radio antenna on GMRS, you may have problems. It's a rare antenna that can do both GMRS and amateur 70cm. An antenna that has low SWR in the amateur radio frequency range will likely have high(er) SWR in the GMRS frequency range, and vice-versa.

[WRYZ926]

I have to agree that most 2m/70cm dual band antennas will have higher SWR reading on GMRS frequencies. Lossy cable and a higher SWR reading on your mobile antenna could very well be what the issue is. Especially if it is a quad band antenna. Multi band antennas are a bit of a compromise in that the bandwidth for each band will be narrower than a mono band or dual band antenna.

A higher SWR will show power loss. Add in poor quality cable will only make things worse.

I run a Comet 2x4SR dual band antenna on my SxS. It is tuned for 2m and 70cm. The 2x4SR is one of the few dual band antennas that have good SWR for GMRS. I get 1.1 to 1.3 on channels 1-22 (462 MHz) and I get 1.8 on repeater channels (467 MHz). A good dual band base antenna that also works well for GMRS is the Comet GP9.

I suggest trying a different antenna instead of the quad band antenna you have now.

[dugcyn]

how did you know i was running quad band antenna?. may have nailed this question but really does an antenna soak power? 

the antenna seams to work well but am not licensed to work them all so do not know tx? still wonder why power would read low on meter.

 

thanks so much for the input.

 

[Sshannon]

2 hours ago, dugcyn said:

antenna in truck is quad band…

 

3 minutes ago, dugcyn said:

how did you know i was running quad band antenna? 

 

[dugcyn]

you also make me wonder if I should go to a simple dual band antenna setup as this is main set up for parking rv in tight spots or oh chit i need coms in the woods. would i be better to have all bands or ones i could tx com on?

thanx for the thought.

 

[WRQC527]

33 minutes ago, dugcyn said:

you also make me wonder if I should go to a simple dual band antenna setup as this is main set up for parking rv in tight spots or oh chit i need coms in the woods. would i be better to have all bands or ones i could tx com on?

thanx for the thought.

 

One more time. What is the make and model of the radio you are using in your truck, and what is the make and model of the antenna on your truck?

[WRUU653]

58 minutes ago, dugcyn said:

would i be better to have all bands or ones i could tx com on?

Having your antenna tuned for the frequencies you Tx on is going to be better for your radio and your communications. 

[WRYZ926]

Without getting too technical, yes high SWR and/or lossy cable can lead to power loss. Basically what happens is power is reflected back down the coax to the radio.

And any multi band antenna is a compromise. While they work on multiple bands, the bandwidth will be narrower on each band. I suggest getting an antenna tuned specifically for GMRS or finding a dual band 2m/70/cm antenna that also has good SWR on the GMRS band.