Disconne Antenna vs Portable ...

[np4r]

Hi , I have a Jetstream Disconne Antena 25-1300mhz in a Tower about 75 feet high . I can copy a lot of signals in Analog and digital uhf/vhf . I was having trouble with a DMR System in the 800mhz range that one of the sites is located near my house so i thought it was a programming issue or scanner malfunction. I bought a 800mhz portable antenna and for my surprise when i tested it next to the disconne (same location) it started to catch a few control channels and new frequencies in 800mhz including the system i was having trouble with. But when i connect again the disconne it goes deaf in 800mhz the signal is full lengh but no decoding. Is there any setup that have to be make to the disconne ? Im thinking about getting a 800mhz outdoor antenna , would it better vertical (ommnidirectional) or directional? Which ones would work greater than the disconne? many thanks for the help !

 

[Hit_Factor]

I would check things like coax and connectors first. What do you have?

 

[Hit_Factor]

what outside antenna do you have ?

It's listed in the original post.

 

[mmckenna]

do you have the top whip installed and if so does it interfere with the reception of other frequencies ?

The top whips add some minimal/narrow VHF low coverage. They serve no purpose on the higher frequencies.

It's well documented that the radiation pattern of discone antennas gets a bit wonky as you go higher in frequency for most of the hobby/ham designs. That could be working against you.
Also, your coaxial cable will have more loss on 800MHz than lower frequencies. That will result in worse performance on the higher frequencies also.

 

[Groeteschele]

Hi , I have a Jetstream Disconne Antena 25-1300mhz in a Tower about 75 feet high . I can copy a lot of signals in Analog and digital uhf/vhf . I was having trouble with a DMR System in the 800mhz range that one of the sites is located near my house so i thought it was a programming issue or scanner malfunction. I bought a 800mhz portable antenna and for my surprise when i tested it next to the disconne (same location) it started to catch a few control channels and new frequencies in 800mhz including the system i was having trouble with. But when i connect again the disconne it goes deaf in 800mhz the signal is full lengh but no decoding. Is there any setup that have to be make to the disconne ? Im thinking about getting a 800mhz outdoor antenna , would it better vertical (ommnidirectional) or directional? Which ones would work greater than the disconne? many thanks for the help !

To receive best signal on 800 MHz frequencies coax should be very best quality especially for a length like 75 feet. Also best antenna should be band specific to 800 MHz signals. Omni-directional or unidirectional would probably depend on signal strength from transmitting tower.

 

[np4r]

HI, RG8-U coax with pl259 connector , i was using that with a hf antenna before (spiderbeam). My Disconne antenna has no whip if you refere to the one that goes at the top of the radials .

 

[mmckenna]

would it help not to install top whip so other frequencies come in better?

I don't know, never tried it. I don't use mine on low band, only VHF high band. I left it on there, had no reason to remove it.

 

[mmckenna]

HI, RG8-U coax with pl259 connector , i was using that with a hf antenna before (spiderbeam). My Disconne antenna has no whip if you refere to the one that goes at the top of the radials .

RG-8 isn't going to do you any favors. Neither will UHF connectors when you get up that high in frequency. You are likely losing most of your signal is coaxial cable losses.

Depending on how long your cable run is, you probably need something like LMR-600 or 1/2" Heliax if you want decent performance up in the 800MHz band.