Discone Antenna connection

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por930
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Discone Antenna connection

Post by por930 » Thu Oct 31, 2013 4:16 pm

I am working out how to connect a Diamond D130J Discone to my RG6 75 ohm Quad cable. I presently have the RG6 Quad cable connected to my BC780HLT scanner by a screw on BNC fitting, then the RG6 Quad Cable runs into my roof cavity to a set of rabbit ears in the peak and works pretty good on the airband, which I want to cover. I can hear all air traffic and most ground traffic ok, but some times the signal a bit weak. I am about 6 kms from the airport tower.

I need to increase the reception strength so I have been offered a Diamond D130J Discone Antenna. The fitting out of the antenna is a SO 239. I need to connect this to my RG6 Quad cable, preferable by a twist on fitting(don't want to buy compressing tool for one job)

Looking at Jaycar etc, and I see some problems in finding a suitable connector, as the matching PL259 connector for the SO 239 output fitting does not seem compatible with RG6 Quad. Maybe I need to run the SO 239, via an adapter to a N fitting? Obviously the more 'adapters', the signal strength will suffer. So, is there a simple connector solution?

Any suggestions?

Geoff

Comint
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Re: Discone Antenna connection

Post by Comint » Thu Oct 31, 2013 5:01 pm

A Discone antenna has NO Gain, so you probably won't see any noticeable difference, if the Discone is mounted in the same location as you have the "rabbit ears".

Also, while 75 ohm N connectors are available, I think you would be hard pressed to find any in Brisbane.

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Comint

SteveO
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Re: Discone Antenna connection

Post by SteveO » Thu Oct 31, 2013 7:18 pm

You can get solder pl259 fittings
Steve

por930
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Re: Discone Antenna connection

Post by por930 » Thu Oct 31, 2013 11:25 pm

Hi
Comint. The plan is to get some height and mount a 2 metre tower on my roof and put the discone on this. According to a radio signal survey, I can almost see the Bne Tower from there, so, should improve reception.

SteveO, Yeah, solder is ok. I am off to Jaycar tomorrow and see what they have.

I can hear all traffic in the air, from most a/c on the ground. Tower comes in loud. But, for some reason, I note that while I hear aircraft on 130.400 and 134.300, I never hear transmissions from airservices. Maybe an issue with my rabbit ears.

I was toying with the idea of building a Jpole from 1/2' copper tube, but being lazy and hoping the discone will do a similar job
Geoff

Comint
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Re: Discone Antenna connection

Post by Comint » Fri Nov 01, 2013 11:47 am

As far as I am aware, Jaycar only sell solder PL259 fittings for RG-8 and RG-58.

There are two problems with this.

1. RG-6 is thinner than RG-8, and thicker than RG-58, and closer in size to RG-59, so won't fit either fitting very well. And Jaycar appears to not sell the appropriate reducer for RG-59 (UG-176).

2. The braid on most RG-6 is aluminium, which means it cannot be soldered to the PL259 connector, so you won't have a good connection right from the start, and it will only get worse over time.

You would probably be better off, dumping the RG-6, which is 75 ohm, and getting some 50 ohm coax with copper braid.

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Comint

por930
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Re: Discone Antenna connection

Post by por930 » Fri Nov 01, 2013 1:57 pm

I sent some time at Jaycar today. The RG6 Quad certainly seems not a common coax used in radios, as far as connectors are concerned.

When I got the Scanner, the seller gave me the RG213 cable that came off it and still had the PL 259 fitted to both ends. Unfortunatly, too short to reach my antenna.

I will never transmit and will mainly listen into the airband range of 118.6 to 134.3, very close to the airport, my Discone will be some 3 metres above my roof on a dedicated mast, with almost line of site to the airport tower, cable run will be approx 25-30 metres. (making sure the antenna is well clear of neighbors trees and above my steel roof) I plan to do the following.

1. Still using my existing RG6 Quad coax, connecting my antenna to a PL259/BNC adapter. Put a BNC RG6 twist on plug on my cable. Now, for far more knowledgeable people I may be committing many sins by this 50/75 ohm mess and it may not work, but for the present, it is my most economical solution as I have some fittings here.

2. Obtain some RG6 Quad PL215 connectors...if this all does not work satisfactorily...

3. Replace my RG6 Quad with some 50 ohm coax, which may simplify the whole connection process.

Anyway Comint, I will let you know how it goes next few weeks or so when I get chance to get on the roof. Meanwhile, my simple in roof antenna seems to do a reasonable job, considering the metal roof has foil insulation, the ceiling has both foil and pink bats insulation.

Geoff

Comint
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Re: Discone Antenna connection

Post by Comint » Fri Nov 01, 2013 4:57 pm

por930 wrote: . . The RG6 Quad certainly seems not a common coax used in radios
Correct. RG6 is specifically designed for Cable TV, and Satellite TV.

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Comint

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Spectre
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Re: Discone Antenna connection

Post by Spectre » Wed Dec 04, 2013 3:14 pm

I use if for all my scanning antenna cable runs, I also reuse/recycle PL259 connectors and have found them easily drilled out to accommodate the added girth of the RG6 cable :mrgreen:

Obvious benefits include...
  • Lower loss figures than comparable 50 Ohm cable
  • Availability
  • Cost
Keep in mind the whole 50/75 Ohm issue has no significance for RX as once you operate beyond the limits of the antenna's design the ohms change anyway...
Equip: Uniden 57XLT, 780XLT, 895XLT, Realistic Pro-2020, Pro-2025 & Pro-2040

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