More power or no hope...

[WRDU469]

I am currently using a KG-935G Plus HT for GMRS comms. It's plugged in to a J-Pole Antenna in my attic via LMR400 with a 1.4 SWR. The feedback I am getting to a repeater about 7 miles away is communications is broken and a bit noisy. Would using a mobile/base station radio with more power help in this case?

Unfortunately I am unable to put this antenna externally on the house. This is what I have to work with.

[marcspaz]

You probably have 2w or less making it to the antenna.  If you switch to a mobile with at least 15w-20w.  That will get you somewhere closer to 10w-12w into the antenna.  A 50w radio will get you about 26w-32w depending on the cable loss.  Multiplying your usable transmit power 13 times will increase your power into the repeater by 4+ s-units, which would be fantastic.  Even at 15w, you will get at least 2 additional s-units into the repeater.

[Sshannon]

2 minutes ago, deltaleader71 said:

Thanks for the information. I have been thinking about a KG-1000G as a base station setup. When testing my SWR, I was getting in excess of 5 watts on the meter. I guess that doesn't mean what is at the antenna, but with LMR 400 on a 40ft run, probably not suffering from a lot of loss. Logically thinking about this, I was leaning toward more power to help get through the wood construction. I might be able to borrow a mobile radio for testing which could be a good first step.

LMR 400 loses about 2.7 dB over 100 feet at GMRS frequencies. So 40 feet would be 40% of 2.7 dB or 1.08 dB so you lose 20.6% of the power your radio inserts into the cable. That’s just the cable loss. That’s really not terrible; it’s just something to be aware of. 
 

[tweiss3]

Also keep in mind, a JPole antenna is not omnidirectional, it has a lopsided pattern. You may be able to rotate the antenna in place to get the pattern to point towards the repeater and reach it better. A mobile radio will be a better option overall though.

[WRDU469]

Thanks for the information. I have been thinking about a KG-1000G as a base station setup. When testing my SWR, I was getting in excess of 5 watts on the meter. I guess that doesn't mean what is at the antenna, but with LMR 400 on a 40ft run, probably not suffering from a lot of loss. Logically thinking about this, I was leaning toward more power to help get through the wood construction. I might be able to borrow a mobile radio for testing which could be a good first step.

[WRDU469]

2 minutes ago, Sshannon said:

LMR 400 loses about 2.7 dB over 100 feet at GMRS frequencies. So 40 feet would be 40% of 2.7 dB or 1.08 dB so you lose 20.6% of the power your radio inserts into the cable. That’s just the cable loss. That’s really not terrible; it’s just something to be aware of. 
 

Good to know! More power would compensate for this loss. I think I need to borrow a mobile radio with power >20 watts and see what happens. I know where I can find one too

[WRDU469]

To close the loop on this thread. I can confirm through testing that I was likely loosing to much power via my HT through the cable run as mentioned by marcspaz. In testing the same setup with a higher power mobile radio, there was a night and day difference in the repeater clearly hearing my communications. The repeater owner verified I had a very good signal. I even learned my HT performed better to this repeater when not plugged in to the attic antenna. This just confirms more power is what I need to get through the attic space. 

Now to figure out which mobile station to setup... 

[Coffeemaker]

I have a similar problem with my attic GMRS antenna.  Even 50 watts doesn't make the trip to the repeater and back any better than an HT in my backyard.  The problem is likely the shingles.  Try a mobile antenna mounted to a gutter on a side of the house with a clear view to the repeater.  It's nice and stealthy and works a charm!

[WRYD530]

Why can you not put up the antenna outside? Hoa? I believe I read somewhere they cannot lawfully stop you from putting up an antenna outside. Anyone else confirm this?

[Sshannon]

1 hour ago, WRYD530 said:

Why can you not put up the antenna outside? Hoa? I believe I read somewhere they cannot lawfully stop you from putting up an antenna outside. Anyone else confirm this?

No, unfortunately that’s not the case. 

[WRKC935]

Hold on for a minute.... before we start looking at more power, lets look at something else.  Namely your receive signal level.

Is the signal coming from the repeater full quieting and strong or is there noise with it?  Do you have a 'bar' type signal level meter on the radio?  If so is the receive signal full bar's or just one or two?  Increasing power output can correct poor signal to a receiver / repeater, but it does NOTHING for your receive.  And having some sort of obstruction between you and the repeater can NOT be corrected with you increasing power. 

What do you know of this repeater?  Is it a high profile repeater on a tower with 200 foot or better antenna height or is it some mail order antenna built in a piece of PVC pipe 12 feet in the air on somebodies garage? 

Is this the only repeater in your area, or are there others?  If there are others, what sort of performance do you get with those other repeaters?  Are those repeaters closer to you or farther away and are they in the same direction from you or different directions? 

Next question, do you have a metal roof on the house or is it shingle?  You are not going to get signal out through a metal roof.  You would be better off to put the antenna in a corner on the highest floor that wasn't in a metal roof if that's what you have.

 

Point is that 7 miles to a good repeater shouldn't be an issue from a handheld radio.  Even a really cheap one.  I am surprised that you even need an external antenna to talk 7 miles to a repeater.  But since you do, I am wondering why that is and if putting more power in the air is going to solve anything.

 

[WRDU469]

Adding more power to my antenna in the attic is what solved this problem for me. The handheld alone can xmit to the repeater with good quality from inside my house, but my reception from the repeater was horrible.  When I applied the HT to the attic antenna, my receive quality improved but the repeater was receiving a much lower quality and broken/staticky signal. This is due to a longer cable run to the antenna and loss of power that resulted. Now that I have a base station setup, the repeater is getting a great signal from me and I am hearing the repeater well. Problem solved.

[dwmitchell61]

Heck, if you have a window you could hang the antenna in, that would shorten the cable run and take the absorption of whatever kind of roofing down quite a bit, also. Composition shingles are coated in pebbles, basically.