[tuning handheld antenna..]

The Nagoya 771 is a dual band amateur band antenna...which judging by its length, looks like a 1/4 wave on 2 meters and 5/8 wave on 70 cm ham band.  I personally would not use this antenna for GMRS.  This antenna would need to see some sort of ground plane to radiate properly, in addition to properly loading for lowest reflected power.  As i am a Motorola person, I am not certain about the construction of the Btech radio in regards to the case acting as a proper ground plane.  If it does not have a metal chassis, or metal impregnated case, and is only relying on the SMA connector for a ground plane, I am not so certain that your goal of antenna trimming will ever be achieved reliably.

[No Ground Plane Antenna for Corvette]

1/2 wave antennas do not require a ground plane.

[Coax Cable Suggestion]

If you are starting out don't fall for the UHF chrome connector trap like I did. Once you start It will be very hard to change to N ..

 

For patch cables, my advice is to go with Harbor Freight RG400, and if you have never crimped anything, have it crimped for you, a bad crimp will hurt more than you think.

 

I would stay away from anything LMR400, or LMR400 equivalent... its a problem waiting to happen, especially if you want to have reliable reception after a couple of years being sitting outside... For a 100 foot feedline I would use Heliax FSJ4-50B, its the same diameter as the LMR400 but none of its drawbacks. And these cables can be purchased N.O.S from places like eBay with factory installed trimetal connectors (low PIM, good impedance match) for a fraction of their original cost. 

 

Buy a base antenna that comes with N connectors. As the UHF connectors will deteriorate over time due not being weatherproof like N. Been there done that.

 

If the radio uses UHF connector, try not to use an adapter, buy an RG400 patch cable with UHF to N.

 

I would do the following:

Radio -> patch cable -> surge arrestor/grounding -> heliax FSJ4-50B -> antenna.

 

Hope this helps.

 

G.

Heliax is the only way to go, especially if in the future, you need to run duplex communication.  When I set mine up, I opted for 7/8" Andrew Heliax, with N- Connectors of course.  I also dived in and acquired a DB420 antenna set up in an omnidirectional pattern.  RG 400 makes perfect patch cabling...double shielded, yet flexible.  My wife had a small coronary when she first saw it up, but she got over it in less than 24 hours.  Antenna, feedline, and grounding are where all the money and effort should be directed.  Do it once and do it right.

[Power Supply and Antenna Suggestion]

You cant go wrong with an Astron power supply, particularly one with a transformer and pass transistors, not a switcher.  I have several Astron's, 35 and 70 amp supplies that are over 20 years old and have never had a single failure.   Mind you, they can be quite a bit heavier weight wise than a switcher, but can handle anything thrown at them.