Wondering if its possible to put my 155mhz tuned stainless steel whip on the radio shack discone in place of the 50mhz that comes with the discone and would it help or not help with the reception of VHF HI band.... don't want to put it up then have it not work... any helps appreciated...
Radio Shack Discone (mod?) replace 50 mhz whip with 155 tuned whip
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prcguy
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It would not help and would probably mess something up at other frequencies. The RS Discone already works about the same as a 1/4 ground plane on 155MHz and adding the whip would possibly load the feed point impedance down around 155MHz and odd multiples. The whip would no longer be resonant at 155Mhz due to the other elements of the disc adding capacitance to the whip at its feedpoint.
A Discone antenna is sometimes referred to as an "aperture" antenna like a horn antenna where it launches a wave from an aperture and in this case its the junction of the disc and cone. Even though the top disc is connected to the hot of the coax it doesn't radiate like a whip would.
The factory whip that resonates around 50MHz has a loading coil at the base which helps decouple it from the circuit at higher frequencies but the whip probably does degrade the performance at some freqs. If you don't need to receive low band its best to loose the whip on top and make it a traditional Discone.
prcguy
A Discone antenna is sometimes referred to as an "aperture" antenna like a horn antenna where it launches a wave from an aperture and in this case its the junction of the disc and cone. Even though the top disc is connected to the hot of the coax it doesn't radiate like a whip would.
The factory whip that resonates around 50MHz has a loading coil at the base which helps decouple it from the circuit at higher frequencies but the whip probably does degrade the performance at some freqs. If you don't need to receive low band its best to loose the whip on top and make it a traditional Discone.
prcguy
Thank you for the answer and I have to use Low Band because our local FD is all lowband. but I figure leave it as is because system is soon to be updates to hi band digital and then I can just lose the 50mhz whip.... thanks so much for your help....
prcguy
Member
The low band whip on these is very narrow band and most I have tested resonated around 50MHz. If your frequency of interest is in the 30-40MHz range then tuning the whip will really perk up receive there.
prcguy
prcguy
I had a friend years ago who actually was the one who got me into radio. He had the radio shack discone antenna. He replaced the top whip with a 102" CB steel whip antenna. He swore by this. He used to go on about how much better his scanner worked by doing this. I have never owned one of these discone antennas. I just know how proud he was of this configuration. Everything he was listening to back then was on VHF. He has since moved away.
wtp
Member
no rules
you can try anything on receive
transmitting is something else
another name for trying is experimenting, it couldn't hurt.
years ago a friend of mine was having trouble receiving 800 mhz using a stock scanner antenna
that was just as 800 was up a coming. the antenna was the old 30 to 512 kind
he did not like the fact that i used a bent paperclip to improve reception (bnc connector)
even a coat metal coat hanger can be an antenna or aluminum foil.
the good old days of rabbit ears. for short wave (.15 to 30 mhz) i used 20 feet of bell wire as a kid
so to recap. try it.
enjoy the chase.
you can try anything on receive
transmitting is something else
another name for trying is experimenting, it couldn't hurt.
years ago a friend of mine was having trouble receiving 800 mhz using a stock scanner antenna
that was just as 800 was up a coming. the antenna was the old 30 to 512 kind
he did not like the fact that i used a bent paperclip to improve reception (bnc connector)
even a coat metal coat hanger can be an antenna or aluminum foil.
the good old days of rabbit ears. for short wave (.15 to 30 mhz) i used 20 feet of bell wire as a kid
so to recap. try it.
enjoy the chase.
LIScanner101
Completely Banned for the Greater Good
Did this improve his VHF low, VHF high or both?
Well it improved his VHF high. That is all there was to listen to around here was VHF high. We did not have and VHF low in the area. The good ole days lol
well I did some experiments over the past 2 weeks... 1 week with the 50 MHz whip and almost 2 days with the 155mhz whip nothing (worst signal ever)
nothing would pick up with antenuator on with 50mhz or 155mhz whip now I am getting close call hits from about 15 miles away with a 150mhz whip from a sn150 by replacing the 50mhz whip on the discone
also has IMPROVED my lo band 46.32-48.4 MHz and noticed today im getting some 850 MHz from about 30 miles away....which is very good seeing im in a valley surrounded by the Adirondack mountains
thanks a lot.. experimenting worked in my case..
ridgescan
Member
I still don't get how the admin hasn't yet deemed you "mentor".
Now I need to get up there and pull that whip off the d130j to see if it'll improve the upper bands. I get CHP in 42megs off the HF wire/r75 anyway.
Again, thanks for a wealth of facts prcguy.
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