Finto
Member
Is there any way to cut the top whip of a discone to improve 800mhz P25 reception?
Discone modification question
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mmckenna
I ♥ Ø
The whip on top has more to do with lower frequency operation. I have a commercial Telwave discone here at work that has no whip on top. It is rated for 100MHz to 3.5GHz.
Trimming the top whip will probably have little effect on the 800MHz reception.
While discones are popular antennas, they are primarily useful for wide band coverage, and that's about it. Zero gain and odd radiation patterns make them not very useful for much else.
Ideally a dedicated 800MHz antenna would be a better choice if that is where you are having issues.
Other option would be to take a close look at your coaxial feed line. Depending on what you are using you could be losing a considerable amount of signal in the cable.
Trimming the top whip will probably have little effect on the 800MHz reception.
While discones are popular antennas, they are primarily useful for wide band coverage, and that's about it. Zero gain and odd radiation patterns make them not very useful for much else.
Ideally a dedicated 800MHz antenna would be a better choice if that is where you are having issues.
Other option would be to take a close look at your coaxial feed line. Depending on what you are using you could be losing a considerable amount of signal in the cable.
KB7MIB
Member
If you don't listen to VHF Lowband, you can remove the top whip altogether.
A dedicated antenna for 700 and/or 800 MHz will give you better reception in those bands.
John
Peoria, AZ
A dedicated antenna for 700 and/or 800 MHz will give you better reception in those bands.
John
Peoria, AZ
n0nhp
Member
Most of the larger ham fests I have visited recently have had several "station master" style 800MHz antennas that have been removed from service.
With the specs for 800MHz coverage most agencies have, signal strength is generally not the problem, I have seen many installations with poor receive made worse by adding a gain type antenna. The front-end of most of the scanners is easily overloaded with out of band signals and multipath signals. A lower gain antenna (quarter wave) and possibly shielding from cell sites can often improve the signal much more than adding more gain.
As everybody above has said, the center whip is for low band (50 to 100MHz) reception only, it does nothing for VHF high and up.
Bruce
With the specs for 800MHz coverage most agencies have, signal strength is generally not the problem, I have seen many installations with poor receive made worse by adding a gain type antenna. The front-end of most of the scanners is easily overloaded with out of band signals and multipath signals. A lower gain antenna (quarter wave) and possibly shielding from cell sites can often improve the signal much more than adding more gain.
As everybody above has said, the center whip is for low band (50 to 100MHz) reception only, it does nothing for VHF high and up.
Bruce
K5MPH
Member
I had a friend do that years ago and it messed the hole antenna up don't do it......
N3JI
Member
I've been meaning to try replacing the top whip with a dedicated 800 MHz whip to see if it did any better -- haven't gotten 'round to it yet though. I've heard it makes a difference, but I want to see for myself...
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