Follow-up to question on base station receive problem

[tjcasper93]

I previously posted a question regarding my base station and how it could transmit well but not receive well.  Since that post I've discovered something.  When I unscrew the antenna about half way I get excellent reception, pulling in several weather stations, some over 100 miles away.  When I do that the SWR goes through the roof at around 5.50.  But when I screw down and tighten the antenna again I lose my weather stations but the SWR drops to 1.17.

 

Any thoughts on how I can keep my SWR low and have great reception at the same time?

[KAF6045]

6 hours ago, tjcasper93 said:

I previously posted a question regarding my base station and how it could transmit well but not receive well.  Since that post I've discovered something.  When I unscrew the antenna about half way I get excellent reception, pulling in several weather stations, some over 100 miles away.  When I do that the SWR goes through the roof at around 5.50.  But when I screw down and tighten the antenna again I lose my weather stations but the SWR drops to 1.17.

 

Any thoughts on how I can keep my SWR low and have great reception at the same time?

Well, one thing to account for: Weather broadcasts are in the 150MHz band -- VHF. Your antenna is specifically tuned for 450MHz band (and maybe even a touch higher since GMRS is 462MHz for receive, 467MHz to reach repeaters). A 1/4wave antenna for Wx would be around 19 inches long, and a half-wave around a yard long. A 1/4wave on GMRS is around 6 inches.

Unscrewing the antenna could (hypothetically): 1) lengthen it enough to hit a somewhat resonant 150MHz (though I've never heard of a 1/8wave antenna , normally one gets a lower band antenna which is a multiple of wavelengths on a higher band); 2) depending upon how the whip mounts, you might be breaking ground-side contact.

As for receiving Weather DX -- If I walk out my kitchen door to the middle of my driveway, I can receive maybe two relatively local Wx stations... If I walk 6 feet in any direction, I receive NONE... 12 feet in any direction and I receive them again... And the pattern repeats. Lay a 12x12 ft grid over my property and I can pick up Wx stations at the grid intersections.

 

 

[tjcasper93]

Thanks, I hadn't thought about the weather station frequencies.  The next time my brother is free we'll try a test with his gmrs radio in his car to see if loosening the antenna on the base station improves reception as he drives out into the country.  This can be maddening at times!