HFU HF Underground

Technical Topics => Equipment => Topic started by: Matt285 on February 09, 2020, 1618 UTC

Title: Discone antenna mounting
Post by: Matt285 on February 09, 2020, 1618 UTC: So as you know most Discone's have the coax point in the center where the mast goes. I need to figure out how I will get the coax in/out of the mast. I guess my question would be, can I use a small length of PVC or does it need to grounded to the mast or grounded in general. Also the connection is different from a standard SO239. It looks like a PL259 would screw in, but when I screwed in a PL259 the center conductor had a loose feel to me. Looks like a type 'N' style. I'm use to using the latter.
Title: Re: Discone antenna mounting
Post by: Brian on February 09, 2020, 2011 UTC: Does it not mount to the side of the mast with 2 u brackets?
You can't screw a PL259 into an N type socket.
Title: Re: Discone antenna mounting
Post by: Matt285 on February 09, 2020, 2013 UTC: Thanks for the reply. I suppose it could be mounted either way come to think of it. Maybe I will thicken up the tip of the center conductor with a bit of solder for a tighter fit.
Title: Re: Discone antenna mounting
Post by: NJQA on February 10, 2020, 0941 UTC: Quote from: Brian on February 09, 2020, 2011 UTC
You can't screw a PL259 into an N type socket.

You can force a PL259 into a female N connector...and you will permanently destroy the female N connector when you do. The center conductor pin will be deformed or broken in such a way that you can’t repair it. Check your antenna for damage.

Something is wrong when you start talking about having to “thicken up the center conductor with solder”. It sounds to me like the antenna is damaged.
Title: Re: Discone antenna mounting
Post by: redhat on February 10, 2020, 1233 UTC: (https://i.imgur.com/8bejAre.gif)

+-RH
Title: Re: Discone antenna mounting
Post by: Matt285 on February 10, 2020, 1345 UTC: I'm not familiar with attaching photos in this set up. I see the option for adding an image or hyperlink, but I'm use to copy and pasting. It looks like a an SO239, but the center portion does not have the standard white insulating material. It's just insulated by open air space. I will work on attaching a photo.
Title: Re: Discone antenna mounting
Post by: Matt285 on February 10, 2020, 1718 UTC: The mounting hardware is all taken care of. I said 'N' connector by mistake. It looks like the center female conductor just needs a slight squeeze with a pair of needle nose pliers. The PL259 will fit fine as far as I can tell.
Title: Re: Discone antenna mounting
Post by: NJQA on February 10, 2020, 1904 UTC: Quote from: IZS4 on February 10, 2020, 1345 UTC
It looks like a an SO239, but the center portion does not have the standard white insulating material. It's just insulated by open air space.

While an N connector will not have the insulating material around the center conductor, most SO239 connectors do...but there is a variant SO-239 that has minimal material, just enough to keep the center conductor socket centered. Most of the dielectric material between the inner and outer conductor is air.

As near as I can tell, this is done to try to make the impedance of the UHF connector closer to 50 ohms. UHF connectors are known to be non-constant impedance connectors (unlike BNC or Type N connectors). The ratio of outer conductor and inner conductor diameters changes across the length of the connector, meaning the characteristic impedance of the connector changes. This is not a big deal on HF, but becomes more of a concern at VHF and above.

I have never seen these connectors for sale anywhere, but have seen them on SWR/power meters, and on VHF and above radios/antennas.

It sounds like your antenna has this variant of a SO239. This would make sense to use with a discone.

Redhat is right - this thread would be a lot shorter if we had included pictures.
Title: Re: Discone antenna mounting
Post by: Matt285 on February 10, 2020, 1941 UTC: Yes. I'll have to figure out how to post photos. It helps a lot in these situations. Yes, i believe it is a variant of of an SO239 as you described.
Title: Re: Discone antenna mounting
Post by: Josh on February 10, 2020, 2031 UTC: Or one could look at the manual.

Wideband reception covering 25-1300 MHz
Transmit bands 26-27-46-49-72-144-220-440-900-1290 MHz
Rust free stainless steel structure
Max power 300 Watts CB / 200 Watts VHF-UHF
SWR <1. 5: 1
1 3/8" maximum mast diameter

UHF female (SO-239) connector

6 lower radials 32 3/4", 2 lower radials 48"-52" adjustable
8 upper radials 11 1/4"
Top whip length 55"
https://www.amazon.com/Tram-1411-Discone-Scanner-Antenna/dp/B00QVNI1V0
Title: Re: Discone antenna mounting
Post by: ChrisSmolinski on February 10, 2020, 2112 UTC: Quote from: Josh on February 10, 2020, 2031 UTC
Or one could look at the manual.

Crazy talk! :P
Title: Re: Discone antenna mounting
Post by: Matt285 on February 10, 2020, 2255 UTC: The manual consist of a double sided piece of paper and does not acknowledge the connector type in any specific way. I'm good to go now. Assembly is pretty straight forward.
Title: Re: Discone antenna mounting
Post by: Matt285 on February 10, 2020, 2259 UTC: Yes. It is an SO239 connector, but not the sort of the typical HF variety. Josh, check your inbox. I have a quick question.
Title: Re: Discone antenna mounting
Post by: nickcarr3151 on February 11, 2020, 0054 UTC: Yes they're using a poor-man's SO239 connector that fits the PL-259 connector. The mount is designed to fit your mast -- use simple emt conduit from Lowe or HD -- and thread the coax thru it and screw down connector. Then you slide the conduit into the base mount and tighten.
Title: Re: Discone antenna mounting
Post by: Pigmeat on February 11, 2020, 0231 UTC: Quote from: ChrisSmolinski on February 10, 2020, 2112 UTC
Quote from: Josh on February 10, 2020, 2031 UTC
Or one could look at the manual.

Crazy talk! :P

Did you know my late FIL, Chris? He managed to leave this life with all of his original parts and he didn't need a stinkin' owners manual. He had dyslexia, it's not like he could read it anyway.