Diamond D-130J

[Deadman]

Currently using Diamond D-130J Discone, with a Uniden BC785D, getting very Low Signals unless i use a Amplifier.
Listening to freq's 60 - 2000Mhz.
Has anybody had a Play with the orientation of the elements, such as Large radials on top, and Smaller ones on bottom, or even a Mix.should I get rid of the whip

I Live in the second largest City in New Zealand, where Most of the VHF-UHF Transmissions are TX'd from the Transmitter on our largest Hill overlooking the city, other transmissions are localised from 10 Storey buildings in the City (Police Building), i cannot receive Transmissions from Distant stations to this Site, only localised.(all transmissions are RX'd at this site for our part of the country).I Have all the Appropiate Frequencies the EMS use, but can't get anything, Nothing yet is in Digital. help is Appreciated
:?:

 

[K2KOH]

One thing you forgot to mention...the type of coax you're using and how long a run of coax you have. Believe it or not, the most important part of the antenna system is the coax. You can have a super duper 20 DB gain antenna on the roof, but if the coax is garbage, your reception will be the same.
I had a discone up with fifty feet of RG6U, good 75 ohm cable, however, I had to use adapters into the radio. I now use LMR 400 low loss, no adapters, and I get much better reception.

Cheers

Kieran

 

[Deadman]

Sorry, I am Using 50 Ohm RG58/c/u. X 8 Meters

 

[astrodanco]

Sorry, I am Using 50 Ohm RG58/c/u. X 8 Meters

Wow, that must be some pretty crappy quality RG-58 if you have to use an amplifier at the antenna to overcome losses with only 8 metres of coax. Are your losses only bad at high frequencies or are they bad at all frequencies? You might replace that cable with something better, such as RG-8X (which is lower loss and amost as small as R6-58; about the same diameter as RG-59) or even better one of the LMR series coaxes. A discone isn't the best antenna for any one frequency either. You might instead invest in separate gain antennas and use a diplexer or triplexer to combine them. Insertion loss can be as low as 0.2db. Diamond has a good one that uses (mostly) N connectors.

 

[K2KOH]

Nah, I think in this case a change of coax will do the trick. I would go with the LMR 400...it's really good stuff, and I think you'll see dramatic change in reception...you more than likely won't need the amp anymore.

 

[NorwalkRXing]

I second the LMR-400 coax...without a doubt, best money i ever spent in this hobby...

 

[CoryCooper]

I am using the same antenna with my BC796D. I am only using some RG8X - Mini that I already had (75' to boot!). I am getting really strong signal strengths in all bands. Could be that my house is on a hill, overlooking the town though!

Cory

 

[MarcTheHague]

The Diamond D-130 is a pretty good alrounder, I've one with the N-connector and I use high quality Ecoflex10 coax.

The performance of the Diamond is pretty good, but above 500 Mhz the reception is in mine opinion not that great.
The specs will tell you a different story ( <1300Mhz ) but is fairly enough impossible for an antenna of this size.

25 .. 250Mhz .. great reception
250 .. 500Mhz .. fair
500 .. 1300Mhz .. poor

Marc .. The Hague, Holland ..
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[cassidy1190]

I am also looking for good cable. About the LMR-400 cable. Does anyone know of a store where I can purchase this? I'd rather take a look at it in person than buy it online. I have had many disapoinments as a result of not doing this :lol:

 

[bsavery]

I am also looking for good cable. About the LMR-400 cable. Does anyone know of a store where I can purchase this? I'd rather take a look at it in person than buy it online. I have had many disapoinments as a result of not doing this :lol:

You prolly won't find it in Circuit City.... but one place to look (if there aren't any Radio shops in the phone book) is companies that specialize in wireless LAN installs. LMR-400 is used in a lot of commercial 802.11b networks.

Bob

 

[Air490]

Better coax seems to be the way to go.

You may find that LMR400, if you can even get hold of it in N.Z., may be expensive (that is the situation in Australia). I find that RG-8 is good, readily available and resonably cheap. The only problem is that it is not very flexible.

Good luck!