Discone D130J vs Diamond Whip RH77CA

Status
Not open for further replies.

benzrider2000

Member
Joined
Oct 31, 2004
Messages
24
I just bought a Diamond discone model # D130J and set it on a pole that goes up about 30 feet or more into the air and it's about the roofline of my house. The strange thing is the Diamond Whip antenna is getting better reception than the Discone!!! I think something definitely has to be wrong.

Can the experts out there in this forum give me some advice on what I might have done wrong?

A couple notes:

1) This discone is specifically for my Bearcat 396T scanner.
2) I have 75' of wire which is about 2.5x as thick as the whip antenna (just for size comparison).
3) Nothing was mentioned about grounding the antenna in the instructions, so I didn't do any grounding of any kind.

Thanks for your time!
 

hoser147

Member
Joined
Dec 17, 2005
Messages
4,452
Location
Grand Lake St. Marys Ohio
You need to ground that antenna. See Wiki for futher info on that. What frequency range do you monitor the most? As far as the coax it should give you the number on the side of the cable every couple of feet. You really cant compare a small whip antenna to one that is outside and up in the air............Hoser
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
23,490
Location
Bowie, Md.
You don't ground a discone - I don't know where that myth got started. Grounding the mast (subject to the local electrical codes) is a very good idea, and a lightning arrestor isn't a bad idea either. We do have a couple of articles in the wiki on the subject.

You didn't say anything about the coax, which is the other part of the equation. 9913 and RG6 coax are going to give you the least loss as you go higher in frequency. Never use the cheap RG58 series - as the freq climbs, so does your loss. Again we have a few things in the wiki that shows this most clearly. Such as...

http://hamradio.arc.nasa.gov/coaxcableloss.html

73 Mike
 

eorange

Secret Agent Man
Joined
Aug 20, 2003
Messages
2,556
Location
Cleveland, OH
I have both of those antennas, and for about a year or so had a 90 foot run of crappy RG58 from the discone to my scanners. It did pretty well, I thought. So that length is not enough to knock your signal out.

Did you check your connectors on each end of the coax? Are they solid?

I used one of those cheap rat shack twist-on BNC connectors which eventually started to give way, and I lost most of the signal. I eventually soldered on a PL-259 connector with a BNC adapter.

PS, I never grounded anything - antenna or coax or myself.
 

benzrider2000

Member
Joined
Oct 31, 2004
Messages
24
The coax I'm using, from what it says on the cable is RG 8X Mini Coax 17 AWG.

Currently, I can't ground the mast because it is not metal.

My connections are solid at both ends.
 

eorange

Secret Agent Man
Joined
Aug 20, 2003
Messages
2,556
Location
Cleveland, OH
Ha, I replaced the RG58 with RG8X (can't remember if it's mini), but same idea. We have the same setup, and my Diamond discone works like a champ.

What is it that you're trying to receive (local police, fire, railroad, marine, air band)? The discone with that length of coax is NOT great on 800 MHz. Then again, neither is the Diamond whip, but the whip definitely does better.

Sorry, I'm at a loss for other ideas. Not knowing anything else, I'd focus on the cable. Check for shorts between the center conductor and the shield, breaks in the jacket where water could have seeped in, and so on.
 

benzrider2000

Member
Joined
Oct 31, 2004
Messages
24
I'm listening mostly in the 42 to 500mhz frequencies, but mainly in the 400's.

All of this equipment is brand new as of yesterday, so I don't think there are any issues with connections, breaks in the wire, etc.

The strange thing is I was listening in the 462 range with my whip antenna and the signal was showing 3 bars, then I changed to the discone, expecting it to max out the bars, and the signal went down to 0 bars, but I could still hear them ok.
 

eorange

Secret Agent Man
Joined
Aug 20, 2003
Messages
2,556
Location
Cleveland, OH
If you have weak discone performance across the entire range of freqs, then it could be an equipment problem (although I hear you about it being brand new).

If not - are you relatively close to any strong transmitter towers? If so, the discone could be picking up too much RF from that tower, causing the 396 to desense and actually seem to lose the signal. Notch filters can help this problem.

Maybe others can chime in - good luck, I'm out of suggestions.
 

benzrider2000

Member
Joined
Oct 31, 2004
Messages
24
I did move the mast and extended it higher and that seemed to help a lot. However, now the pole i'm using really sucks. It bends over at the top with the discone attached.

Can anyone recommend a 30' telescoping mast that can hold a discone antenna?
 
Status
Not open for further replies.
Top