Vertical Antenna ?

SWLing and TX Forum, for everything below 30MHz...

Vertical Antenna ?

Postby 742-xx » Sun Jun 04, 2017 4:57 am

After quite a while playing with end-fed random wire antennas I'm looking at something a little more 'permanent'.
Up to now I've been using two 30 feet fibreglass poles and about 90 feet of wire, which I put up when Iwant to use the radio and put away when I'm finished.

I've been looking at the SIGMA Ham Radio Antenna SE-HF-X80 VERTICAL RADIAL. This retails at about £85. However, one review suggested it's nothing more than a CB antenna which has been renamed and had its price trebled !
I think this is the CB antenna they're referring to - Sigma Venom 1/2 Wave. This retails at £24.

So, finally to the question ! I only want to recieve - I have no interest in transmitting. Would the CB antenna be any use for HF?
742-xx
 
Posts: 14
Joined: Fri Nov 13, 2015 9:15 pm

Re: Vertical Antenna ?

Postby m0lsx » Sun Jun 04, 2017 10:19 am

Hi...Those short end fed antennas are a big compromise. I have a homemade wire variation of the Sigma.
The original & best commercial versions of these antennas were made by Snowdonia & at much better prices that Sigma are selling them for.
My variation of this antenna is a short wire that is designed to be taped to the side of a fiberglass roach pole for portable operation & it has a connection point at the balun for counterpoises.
These vertical multi band antennas like the Sigma are normally cheap half or 5/8th wave CB antenna minus the loading coil. So they are not good at 10 meters as they have lost the required loading coil & get electrically shorter & shorter on every other HF band. IF you load these antennas at the base with a remote tuner they become half reasonable due to the lack of coax loss & IFyou add plenty of counterpoises they become a good compromise.
Nigel, M0CVO use to do, (& may still do) a Balun with two SO-239's to fit to the bottom of your own CB antenna if you want to use your own CB antenna. And these are often available for free via sites like Freegle/ Freecycle upon request.
But compared to something like a ZS6BKW it is a very poor antenna.
A ZS6BKW is similar to a G5RV. But unlike the G5RV it is resonant on several different bands & a good RX antenna. The G5RV is a 20 meter antenna that is a compromise antenna else where & which is renown for being deaf.
If you have limited space or if you want a fold up portable vertical for occasional use then a CB multi band antenna can be a good choice. My wire version for example can be more easily hidden in a tree, or taped to guttering or laid on a roof. But without some counterpoises, do not expect it to work very well & what ever you do put plenty of ferrites on your coax or add a 1:1 balun as the Coax will give you all sorts of issues in the shack other wise.
I know some of the ex CB brigade use ugly baluns. But on a multi band antenna these are not ideal as each band has it's own requirements & it also draws extra attention to your antenna by neighbours & it adds a lot of extra weight to your solder joint at the PL-259, especially on windy days & unlike a 1:1 you cannot tape it to your mast. As that will alter it's resistance value.
A 10 to 30 MHz air wound (Ugly) choke takes around 17 feet of Coax on a 4 inch former. Imagine that swinging around in the wind. On the other hand a small waterproof box with 5 feet of coax wound around a ferrite core achieves the same results & is far better results multi band..
Take a look at..
http://www.karinya.net/g3txq/chokes/

Image
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via https://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
73 De Alan (M0LSX.)
http://www.qrz.com/db/M0LSX"
User avatar
m0lsx
 
Posts: 5363
Joined: Wed Nov 21, 2012 9:14 pm
Location: Norwich. TG21.

Re: Vertical Antenna ?

Postby 742-xx » Sun Jun 04, 2017 1:56 pm

Thank you for your, as always, very full answer.
When I finished work this morning I did get 20 feet of speaker wire (the same length as the CB antenna) and fastened it to a fibreglass pole that I use, I also used a balun I have from another wire antenna I have. I put this half way down the garden and I'm not sure if I was just lucky with the conditions but I got some strong contacts on 7mhz.
So as always it's a case of experimenting with what actually works where I am.
Thanks again.
742-xx
 
Posts: 14
Joined: Fri Nov 13, 2015 9:15 pm

Re: Vertical Antenna ?

Postby 742-xx » Tue Aug 22, 2017 5:31 pm

Well, I bit the bullet and got a Sandpiper MV-10.
I've tried it a few times and it's very poor. Up to now random lengths of wire - from 20 foot to nearly 90 foot consistently outperform it.
I wanted a vertical which would stay in position in my garden all year round. This is not the one.
The quality is on par with the Sigma aerial I bought as an experiment. The Sigma cost £35 - the Sandpiper £185.
Anyone considering one of these, don't bother.
Back to the wire !
742-xx
 
Posts: 14
Joined: Fri Nov 13, 2015 9:15 pm

Re: Vertical Antenna ?

Postby G4RMT » Wed Aug 23, 2017 8:37 am

As a vertical is unbalanced, the coax is unbalanced and the radio is too - why did you use a balun? Unless you need the balancing properties, which you don't appear to, it's quite a lossy and band limiting component?
G4RMT
 
Posts: 1103
Joined: Sat Feb 07, 2015 5:45 pm

Re: Vertical Antenna ?

Postby m0lsx » Wed Aug 23, 2017 1:46 pm

G4RMT wrote:As a vertical is unbalanced, the coax is unbalanced and the radio is too - why did you use a balun? Unless you need the balancing properties, which you don't appear to, it's quite a lossy and band limiting component?


Normal SWL protocol, if using a so called balun, is to actually use a 9:1 un/un, but it's called a balun, like anything from a air wound choke to a real balun. An un/un gives two advantages. One is an electrical break between antenna & radio reducing noise levels a little & secondly an opportunity to feed against an earth stake rather than radials, as again this again reduces noise levels a little. SWL's unlike amateurs only have RX to consider so all that matters is the noise to signal ratio.
For an SWL an S9 signal knocked down to S2/3 is no issue, especially if it's readability increases from 2/3 to 5.
A balanced tuner with ladder line feeding a wire is another option, again this gives good noise to signal performance.
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via https://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
73 De Alan (M0LSX.)
http://www.qrz.com/db/M0LSX"
User avatar
m0lsx
 
Posts: 5363
Joined: Wed Nov 21, 2012 9:14 pm
Location: Norwich. TG21.

Re: Vertical Antenna ?

Postby 742-xx » Wed Aug 23, 2017 3:53 pm

The one good quality of the Sandpiper is the lack of noise compared to the random wires. I also use two 48inch copper earth rods.
The Sandpiper is probably best described as a 'work in progress' in my particular case. I have to say though that my overiding feeling is disapointment.
I understand that verticals work best for DX but up to now it's not good at that either. Perhaps it's weather and conditions, time will tell.
742-xx
 
Posts: 14
Joined: Fri Nov 13, 2015 9:15 pm


Return to HF & Shortwave

Who is online

Users browsing this forum: No registered users and 2 guests