BC75XLT Antenna Questions

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Jimwheel

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I purchased my Bearcat BC75XLT 01/11/2014 and I am trying to learn how to use it.
I built the "Off-Center Fed Dipole"
"http://wiki.radioreference.com/index...ter_Fed_Dipole"
Using 48" & 18" PCV pipe wrapped with Aluminum Foil (48" up) and Radio Shack #15-1140 reception was good.
I then switched out the 48" with another 18" reception was not as good.
I would like to build 48" & 18" using copper pipe for my perament antenna.
Can I use 1/2" pipe or do I need to use 3/4" pipe?
Do I need to paint it?
I just want a good antenna to scan the following:
151.43000,152.99000,153.53000,154.17500,154.20500,154.31000,154.78500,154.99500,155.05500,155.13000,155.14500,155.24250,155.34000,155.89500,155.94000,158.13000,159.85500,160.02000.
Any help and suggestion will be greatly appreciated.
 

popnokick

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For the narrow range of freqs you listed 1/2" pipe is adequate. It will work at least as well... Maybe better... Than your foil-wrapped PVC, Use whichever. No need to paint it.
 

Jimwheel

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The foil-wrapped PVC was to see if I could receive anything. Now that I can receive I want to build something good and permanent. Do I need the end caps on the pipe, are they just for show?
Would you suggest something difference?
 

popnokick

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Same with the end caps as the paint: unnecessary to the operation of the antenna. If its non-conductive, its not going to affect reception, bandwidth, etc.
 

nanZor

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I then switched out the 48" with another 18" reception was not as good.
Yes - you basically had a center-fed dipole resonant at around at 150 mhz, BUT you would also want to remove the transformer and attach directly to the coax instead as it is no longer needed.

That would do fine for your vhf-hi freqs, and actually be a better performer since it is designed for a narrow(er) frequency range using the standard baseline dipole.
 

Jimwheel

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Want to make sure I understand you correct.
It would be better to use the copper 18"/18" without the transformer than the copper 18"/48" with the Transformer?
 

popnokick

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For the closely-spaced list of VHF high band frequencies you listed... Which did not include any VHF low band, 800 mHz, or other UHF... Then yes, a regular dipole (equal length legs on each side of feedline) is going to offer better performance than an OCFD. If you attempt to tune frequencies that are not VHF high band then do not expect much from the VHF high-tuned dipole.
As hertzian noted, remove the balun transformer if you build the regular dipole and attach the coax directly to the antenna elements (one to center conductor, one to shield/braid). A regular dipole has a feed point impedance close to 50 ohms... And should be used with 50 ohm cable and no transformer. Can you use 75 ohm cable that you already have? Maybe, but keep it simple and match antenna impedance to cable.
The OCFD has a feed point impedance near 300 ohms, which is why it requires the matching transformer to bring it to 75 ohms for your RG6 coax and receiver matching.
 

Jimwheel

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Is 18" the best length or some other length?

Regular dipole (equal length legs on each side of feedline) is going to offer better performance.
Is 18" the best length or some other length?

Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 7_0_4 like Mac OS X) AppleWebKit/537.51.1 (KHTML, like Gecko) Version/7.0 Mobile/11B554a Safari/9537.53)

For the closely-spaced list of VHF high band frequencies you listed... Which did not include any VHF low band, 800 mHz, or other UHF... Then yes, a regular dipole (equal length legs on each side of feedline) is going to offer better performance than an OCFD. If you attempt to tune frequencies that are not VHF high band then do not expect much from the VHF high-tuned dipole.
As hertzian noted, remove the balun transformer if you build the regular dipole and attach the coax directly to the antenna elements (one to center conductor, one to shield/braid). A regular dipole has a feed point impedance close to 50 ohms... And should be used with 50 ohm cable and no transformer. Can you use 75 ohm cable that you already have? Maybe, but keep it simple and match antenna impedance to cable.
The OCFD has a feed point impedance near 300 ohms, which is why it requires the matching transformer to bring it to 75 ohms for your RG6 coax and receiver matching.
 
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