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Scanner / Receiver Antennas For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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Old 03-23-2014, 9:27 PM
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Default Need Matching Transformer??

I'm new here. Still learning. Simple question: If I wanted to use the Diamond D130J discone with RG-6 quad shielded cable, do I need a matching transformer to convert the 50-ohm output of the antenna to the 75-ohm nature of the cable?

If so, what transformer should I use? Or will the Radio Shack F to PL-259 adapter (model 278-258) be sufficient? My cable run is about 60-feet, give or take, and I might add an inline amplifier after I see how it works without one initially. Going to use with SDR & ADS-B, initially, and then with a BCD-436HP in a month. (I know RG-6 isn't the best cable, but I'm going to give it a try and learn as I go.)
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Old 03-23-2014, 9:31 PM
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No, you don't need a matching transformer. The impedance mismatch is small, and you wouldn't notice the difference. Even if you were transmitting, you wouldn't have an issue. Just connect it up and go.

RG-6 is fine if that is what you have. You can always upgrade later.
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Old 03-24-2014, 2:02 AM
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Quote:
Originally Posted by mmckenna View Post
RG-6 is fine if that is what you have. You can always upgrade later.
Thank you. Another question: What do I put at the end of the RG-6 that I'm going to screw onto the D130J? All the crimp-on male SO-239 connectors I'm finding are designed for other cables (RG-58/U, RG-59/U, RG-62/U). Should I use one of those, or should I be looking for an SO-239(male)-to-F(female) adapter?

(And, if I'm better off buying the D130NJ (uses the N connector), I haven't purchased the antenna, yet.)

Last edited by JinLV; 03-24-2014 at 2:11 AM.. Reason: typo re: gender of plug
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Old 03-24-2014, 9:54 AM
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Quote:
Originally Posted by JinLV View Post
Thank you. Another question: What do I put at the end of the RG-6 that I'm going to screw onto the D130J? All the crimp-on male SO-239 connectors I'm finding are designed for other cables (RG-58/U, RG-59/U, RG-62/U). Should I use one of those, or should I be looking for an SO-239(male)-to-F(female) adapter?

(And, if I'm better off buying the D130NJ (uses the N connector), I haven't purchased the antenna, yet.)
It is possible to find PL-259 connectors that will fit on RG-6 cable, but they are not common. Back in the 60's, some TV distribution systems used the "UHF" type connectors, but that hasn't been standard in a very long time. In reality, a good adapter will not be noticeable in your system, and it will be easier to find.

As to which antenna, it's up to you. I prefer type N connectors as they are more standard in the industry, and a properly installed N connector is waterproof by design. A UHF (SO-239) connector will work just fine. Just make sure you weatherproof everything that's outside. Water intrusion into your connectors will allow the water into the coaxial cable. That will degrade performance, then likely fail. An ounce of prevention is worth a pound of cure.
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Old 03-24-2014, 10:10 AM
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Unless you have a very good source that I do not about, finding 239 connectors to go directly on RG6 is impossiale to find.

There are very good 'f' connectors and even BNC connectors available. Just be sure you get the compression type and not the el cheapo type.

After you install the 'f' connector or even the BNC there are adaptors to go to N or UHF.
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Old 03-24-2014, 11:44 AM
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I prefer type N connectors as they are more standard in the industry, and a properly installed N connector is waterproof by design..
Thanks. I'll go with the N-connector, then. I am aware they're better quality connectors. Any words of advice on how to insert the N connector? I've been told if you attach the N connector improperly, you irreparably damage the antenna. I'm generally very careful, but the person that warned me left me with the impression it can happen easily.
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Old 03-24-2014, 12:24 PM
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Quote:
Originally Posted by JinLV View Post
Thanks. I'll go with the N-connector, then. I am aware they're better quality connectors. Any words of advice on how to insert the N connector? I've been told if you attach the N connector improperly, you irreparably damage the antenna. I'm generally very careful, but the person that warned me left me with the impression it can happen easily.
Can't say I've ever heard of that. They only go in one way. They should go together snug. Maybe if the pin or something was out of alignment….
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Old 04-01-2014, 1:27 AM
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Antenna is up and cable is run, but I'm not receiving a signal because I have the wrong F81 coax connector joining two RG6's in the attic. It's the 3GHz kind intended for satellite TV. I'll replace it with a more suitable one.

Questions:
1. When I see connectors and splitters for "5 MHz to 1 GHz", will they pass through frequencies like 1090 MHz or even 1200 MHz? (Technically, they're higher than 1GHz, but I can't believe the frequencies stop at 1,001 MHz.).
2. What's a good brand/source with minimal loss for a single F81-type connector but also a 1-to-3 or 1-to-4 splitter I'll need at the end of the cable run for 2 or 3 RTL dongles and one scanner?
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Old 04-01-2014, 7:51 AM
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The F81 type F barrel adapter with the blue dielectric is the best and will work from DC through 3GHz, no need to change it. CATV type connectors and adapters rated to 1GHz will work past 1GHz but can have problems at spot frequencies, especially when you have several in the system where a particular frequency is affected and compounded by the additional connectors.

A Diamond DJ130 is probably not the best choice for ADS because after about 500Mhz the antenna pattern shifts upward and has a bunch of lobes and nulls making reception unpredictable.

Contrary to what some people think, for aircraft reception you want the most gain at the horizon and not up in the air. When aircraft are at high altitude they are usually very line of sight for quite a distance and easy to receive with almost no antenna. When they get 50-100mi or more away they are getting down to the horizon and trees, buildings, etc start getting in the way and more gain down low is good.
prcguy

Quote:
Originally Posted by JinLV View Post
Antenna is up and cable is run, but I'm not receiving a signal because I have the wrong F81 coax connector joining two RG6's in the attic. It's the 3GHz kind intended for satellite TV. I'll replace it with a more suitable one.

Questions:
1. When I see connectors and splitters for "5 MHz to 1 GHz", will they pass through frequencies like 1090 MHz or even 1200 MHz? (Technically, they're higher than 1GHz, but I can't believe the frequencies stop at 1,001 MHz.).
2. What's a good brand/source with minimal loss for a single F81-type connector but also a 1-to-3 or 1-to-4 splitter I'll need at the end of the cable run for 2 or 3 RTL dongles and one scanner?
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Old 04-02-2014, 1:02 PM
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Quote:
Originally Posted by prcguy View Post
The F81 type F barrel adapter with the blue dielectric is the best and will work from DC through 3GHz, no need to change it.
Thank you. You're right. I spent more time changing settings with SDR and it appears I'm getting signals from the antenna.

When I get around to adding a splitter (using F-connectors) to drive multiple RTL's, which one would you recommend?
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