EMRFD Message Archive 13743
Message Date From Subject 13743 2017-04-01 21:28:05 skipp025 Trying to ID simple dual band vhf/uhf antenna article re: Trying to ID simple dual band vhf/uhf antenna article (QST Magazine maybe?)
Hello to the group,
I'd like to ask if anyone can remember and help me locate a a simple dual band
antenna construction article as I will now try to describe, probably from QST Magazine
from at least a few years back.
A standard VHF 2 meter spike (approx 17 to 19 inches long) was the basic building
block. The added UHF portion of the constructed antenna is/was a length of rod or
solid wire soldered on to the spike starting about half or 2/3 up from the base mount.
From memory, the added UHF wire segment length was less than the VHF main
rod/element. The added (soldered) on UHF wire segment initially went up and then
was bent (folded) over and pointed down until it ended, with the end at least a few
inches above the main rod base.
This antenna was really simple to make; if I can find the article, I'm going to try and
reproduce it. If it works well enough, the local Ham Club might add it to a Saturday
group build-fun day project list.
Thank you in advance for any replies.
skipp025 at yahoo dot com
13744 2017-04-01 23:10:31 Tom Noll Re: Trying to ID simple dual band vhf/uhf antenna article Hi OM Skip,I seem to recall such a dual-band J-Pole type arrangement in QST a number of years ago. A search on the arrl archive might well succeed (not a member now, so I lack access). Not sure, though, since that's not exactly a spike. It did look easy to build.GL and 73,Tom 13745 2017-04-01 23:18:29 Ashhar Farhan Re: Trying to ID simple dual band vhf/uhf antenna article it took me 10 seconds to find it! :-)- f 13746 2017-04-01 23:49:29 Dana Myers Re: Trying to ID simple dual band vhf/uhf antenna article 13747 2017-04-02 00:31:27 Andy Re: Trying to ID simple dual band vhf/uhf antenna article There are many versions of this J-pole. Some use copper pipe, where the quarter-wave matching section is the only part that sticks out and it's shorter than the rest of it. That might be what you remember seeing. It wasn't the "UHF portion"; it's actually the matching stub.The thing about many (most?) 2m antennas is that they simply happen to be resonant in the 70cm band as well, since it's the 3rd harmonic. But the radiation in the 70cm band is much less than ideal, tending to send quite a bit of your energy skyward which doesn't help. Most of these "dual band" J-poles ignore that fact, perhaps because they never looked at it, and the VSWR looked good so why bother.There's a guy (Edison Fong?) who also had a pair of articles in QST where he describes what he did to fix that problem.Andy 13748 2017-04-02 06:20:27 Mike Re: Trying to ID simple dual band vhf/uhf antenna article And if you can consider a dual-band quarter wave vertical rather than a
J-pole, here's a very simple "cheap" option:
I built one of these using a teflon insulated, silver plated 4-hole
SO-239, with copper-clad #14 for the radiators and radials, and coated
the external solder connections with liquid electrical tape, and it's
still going strong at my house after about 5 years. It probably does
not have the better-defined radiation pattern and gain characteristics
that a J-pole would have, but it was very easy to construct- took me a
Mike Dinolfo N4MWP
13749 2017-04-02 08:17:10 Phil Sittner Re: Trying to ID simple dual band vhf/uhf antenna article
Take a look at the March, 2017, issue of QST. The author, Edison Fong, WB6IQN, details a triband version of his popular J-pole design and provides insight into his design process. You can eliminate the 220 element without affecting the other bands. I have built a few of these antennas and caution you, as does Edison, that twin lead varies dramatically between vendors, and even between the same vendor's batches. The antenna's resonant point shifts dramatically once inserted into a piece of PVC due to the change in dielectric constant. If you have access to a VNA it will greatly simplify the construction process. It is a really good antenna and a bargain considering the price.
13750 2017-04-02 08:43:06 skipp025 Re: Trying to ID simple dual band vhf/uhf antenna article > Trying to ID simple dual band vhf/uhf antenna articleHello again,
> ... recall such a dual-band J-Pole type arrangement in QST a number
> of years ago.
> .. since that's not exactly a spike. It did look easy to build.
First off, a sincere thank you to everyone who replied... but the J-Pole articles
are not what we are looking for.
The J-pole antenna is exactly what we're trying to avoid in this case.
Picture a traditional VHF quarter wave spike antenna on the roof of a police
car or fire truck. Then a small piece of gas brazing rod (making up the antenna's
UHF portion or matching section) was bent in to a J form, then inverted and
the short end at the curved end of the J was soldered to the spike about 2/3 to
3/4 up from the base. I believe this really simple dual band (probably mobile)
antenna appeared in a QST article at least a few year back.
So... We are still looking for a reference and/or copy of that article.
Again, thank you to everyone who has already replied and those who will
hopefully do so with a lead to this elusive antenna aritcle.
skipp025 at yahoo dot com
13751 2017-04-02 08:46:52 Dana Myers Re: Trying to ID simple dual band vhf/uhf antenna article 13752 2017-04-02 10:06:45 Jim Anderson Re: Trying to ID simple dual band vhf/uhf antenna article This is a 3-band model from a 37 year old QST article but it looks similar to what you're describing. Perhaps you could adjust the dimensions to provide a dual band model. Or, if you have 220 activity in your area, you could use it as-is.73, Jim - K0RGI 13753 2017-04-02 10:11:21 kb1gmx Re: Trying to ID simple dual band vhf/uhf antenna article Correct that's not a Jpole its a variation of a Latten Trap.The idea is to add an antenna on a lower frequency antenna such as a 2M 1/4 wave thenadd a element at the correct RF point to make the antenna work at 440 as well.FYI a standard 2M monopole (whip) is ok at about 420 and usable at 440 but matterscan be improved.For mobile use the more stuff you hang off the whip the more likely it will break. Wind resistance.Allison 13754 2017-04-02 16:02:20 Cecil Bayona Re: Trying to ID simple dual band vhf/uhf antenna article Unfortunately the majority of hams do not belong to the ARRL so the link
is useless to them.
13755 2017-04-02 17:45:21 Jim Anderson Re: Trying to ID simple dual band vhf/uhf antenna article Hopefully the OP is a member. As the American Express commercials from around the same time as the article used to say, membership has its privileges. I find the archive and search to be a great benefit and keeps me from stockpiling years and years of QST. 13756 2017-04-02 22:32:42 skipp025 Re: Trying to ID simple dual band vhf/uhf antenna article > Hopefully the OP is a member. As the American Express commercialsThe Op is a member and I received the ariticle in pdf after logging in. Again,
> from around the same time as the article used to say, membership has
> its privileges. I find the archive and search to be a great benefit and keeps
> me from stockpiling years and years of QST.
thank you to everyone, but it's not the exact article I was looking for. I believe
the article was probably not more than 10 years back at the most... but time
thanks, I'll keep looking around.