SWR Discone antenna

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Timbo01

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I have recently installed a Diamond Discone antenna . And I am having worse reception than using the stubby antenna on my UBCD396XT.

1. Does an antenna like this have to be SWR ed in?
2. Is the RG6 cable a problem?
3. I read somewhere that the whip antenna on top of the Discone should be trimmed bit by bit till it works properly.

The Discone Antenna has a female PL-259 fitting so I used the applicable male connector..
However these were screw on fittings and I not sure if leaving the foil and surrounding wire shielding has to be removed before screwing the connector on or is the copper wire shielded from this some how when soldered into the plug pin?

If you can give some advice it would be greatly appreciated. As I am becoming quite frustrated with the new toy/setup.
 

ermin

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Dec 21, 2007
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358
Location
Jacksonville Florida
I have recently installed a Diamond Discone antenna . And I am having worse reception than using the stubby antenna on my UBCD396XT.

1. Does an antenna like this have to be SWR ed in?
2. Is the RG6 cable a problem?
3. I read somewhere that the whip antenna on top of the Discone should be trimmed bit by bit till it works properly.

The Discone Antenna has a female PL-259 fitting so I used the applicable male connector..
However these were screw on fittings and I not sure if leaving the foil and surrounding wire shielding has to be removed before screwing the connector on or is the copper wire shielded from this some how when soldered into the plug pin?

If you can give some advice it would be greatly appreciated. As I am becoming quite frustrated with the new toy/setup.
Hello

Here's the scope!

1. No. should not be a problem.
2. That should be great . How long is the coax?
3. No. Only if your going to transmit around 50 to 54 Mhz.

If you can get to both ends of the cable with the connectors at the same time try this. (you'll need a volt-ohm meter. You should be able to get one for under $10 if you or someone you know doesn't have one.)
Testing the connectors you SHOULD have continuity center pin to center pin both ends. Outer conductor to outer conductor both ends. NO CONTINUITY center pin to outer conductor, either end.

You'll probably find out you have a short (continuity between shield and center conductor) or an open (no continuity) between both ends either in the center conductor or the shield. Please let us know what you find.

73

Ermin
 

joeuser

The Wretched
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Feb 9, 2014
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North Central Kansas
I have recently installed a Diamond Discone antenna . And I am having worse reception than using the stubby antenna on my UBCD396XT.

1. Does an antenna like this have to be SWR ed in?
2. Is the RG6 cable a problem?
3. I read somewhere that the whip antenna on top of the Discone should be trimmed bit by bit till it works properly.

The Discone Antenna has a female PL-259 fitting so I used the applicable male connector..
However these were screw on fittings and I not sure if leaving the foil and surrounding wire shielding has to be removed before screwing the connector on or is the copper wire shielded from this some how when soldered into the plug pin?

If you can give some advice it would be greatly appreciated. As I am becoming quite frustrated with the new toy/setup.

1. No. 2. Doubt it, no 3. Unsure, someone else will answer that

Leave the foil in place, think of it like shielding, it should slip over the connectors boot. This way the boot slides inside the shielding and the shielding is outside the boot.

You Discone placement could be the issue also. Where is it mounted, what is it mounted to, is it grounded? Etc...
 

prcguy

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So Cal - Richardson, TX - Tewksbury, MA
The whip on top of the Discone is usually factory tuned around 50MHz and trimming it will only affect 50Mhz range. The actual Discone has no tuning and should work fine from about 100 to 800MHz but above about 500MHz the pattern points upward and is not so good for 800 reception.

If you installed your own connectors and are not familiar with that I would suspect your problem is in the cable/connector junction. I don't know of any PL-259 connectors that work directly with RG-6 and most RG-6 has a foil shield and a token braid that does not take solder very well.

You can get PL-259 to type F adapters and just put good quality F connectors on your RG-6 and use an F to BNC or other adapter at the radio end. How long is your cable run?
prcguy



I have recently installed a Diamond Discone antenna . And I am having worse reception than using the stubby antenna on my UBCD396XT.

1. Does an antenna like this have to be SWR ed in?
2. Is the RG6 cable a problem?
3. I read somewhere that the whip antenna on top of the Discone should be trimmed bit by bit till it works properly.

The Discone Antenna has a female PL-259 fitting so I used the applicable male connector..
However these were screw on fittings and I not sure if leaving the foil and surrounding wire shielding has to be removed before screwing the connector on or is the copper wire shielded from this some how when soldered into the plug pin?

If you can give some advice it would be greatly appreciated. As I am becoming quite frustrated with the new toy/setup.
 

n5ims

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Jul 25, 2004
Messages
3,842
1. Does an antenna like this have to be SWR ed in?
SWR is something that's associated with transmitting, not receiving (it's the ratio of signal being transmitted vs. signal being reflected back to the transmitter) so it's not something that's applicable to a receive-only situation.

2. Is the RG6 cable a problem?
Perhaps, but for moderate runs - 50 to 75 feet long or so - it should work fine. Be aware that my statement is based on using quality cable with properly installed connectors. Cheap cable and cheap or badly installed connectors will negate my response.

3. I read somewhere that the whip antenna on top of the Discone should be trimmed bit by bit till it works properly.
The whip on the top is only used for the VHF-Low (30 - 50 MHz) band reception. If you're using it to receive on this band, you may need to tune it, but if not it will have minimal or no affect.

The Discone Antenna has a female PL-259 fitting so I used the applicable male connector..
However these were screw on fittings and I not sure if leaving the foil and surrounding wire shielding has to be removed before screwing the connector on or is the copper wire shielded from this some how when soldered into the plug pin?
Screw on connectors are not very reliable and can easily cause issues. Also, RG-6 is designed for crimp on type connectors (generally "F" connectors are used) and will generally work better. You will need an adapter (Female "F" to Male UHF for your antenna) to handle the connection for you. The center conductor should go to the center pin on your connector and the shield (that foil and wire braid) is connected to the outer part of the connector. The foil should be cut back, just enough so it doesn't contact the center connection and the braid connected securely to the outer part of the connector.

I have recently installed a Diamond Discone antenna . And I am having worse reception than using the stubby antenna on my UBCD396XT.

...

If you can give some advice it would be greatly appreciated. As I am becoming quite frustrated with the new toy/setup.
First comment: The Diamond Discone is a pretty good wide band antenna, but be aware it has no real gain. The design is to provide you with a wide frequency range, not a powerful signal. Since the gain is low, it's important that you use quality low-loss coax that's as short as you can make it.

Second comment: You don't say what frequency of frequencies you're trying to pick up. The higher the frequency, the harder it is to get a good signal from the antenna to the radio. You may be able to optimize a solution for a narrow band of frequencies (say a single band) by using an antenna designed specifically for that range.

Third comment: It's possible that you may have too much signal (yes, that's possible). Generally this is due to a simulcast system and getting strong signals from multiple towers. It's also possible that the new antenna may be picking up other strong signals (broadcast radio, TV, paging, cell phone signals, or other signals) that are drowning out the ones you're trying to monitor.

If you would provide your location and what you're trying to monitor (not "my local PD" but more specifically like "The Podunk ID PD on 155.325 MHz and their trunked system, the Podunk ID Public Safety System" and if possible, provide links to them from the RR Database). This will help us identify possible problems and perhaps a local user may recognize the issues and help to provide specific suggestions to help you out (e.g. "The Podunk PD's Tac-2 channel is dual-use and each has their own tone. If you program it as CSQ - no tone programmed - you'll pick up any transmission on that channel").
 
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Mile High, or more.
Not sure where all of the VSWR talk got started in the monitoring community. It's irrelevant. Same with "Gain". These are traits dealing with transmission.

I have a couple of the same antennas you are using. They hear great on all bands, and for transmitting, I get a flat VSWR across all of the bands I'm authorized use of. (Ham, and UHF and VHF EOC freqs) I use them in public service events. Quick and easy setup, with coverage on any freqs we need to use.

Check those connectors and feed line.
 

SCPD

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I am using a Diamond Discone mounted about 40' up my tower. I used soldered connectors and low loss RG-8 type coax. It works fine.
 

Timbo01

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Discone Antenna

Thanks very much for your replies. I will check to see if there are any shorts. and if necessary refit/change the connectors.I am scanning with a UbCD396xt. and am interested in mainly between 100-600 mhz. The RG6 coax is about 22metres long.

Also I recently used the Freescan program and removed a lot of inbuilt factory frequencies. The police channels I used to scan used to displat as NFM when I could read them,now i get nothing and it displays as BFM. But I am prepared to perservere and manually enter the frequencies rather thn download massive amounts .

Iam also confused regarding Site. I understand that you create a system and then a group within the system, but what is the SITE? Are the transmission towers for the groups?

Anyway Thankyou

Timbo01
 
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