...and then there is the poor old Elk Log-periodic with 1 feed line, no duplexer on the antenna and a whole lot of gain !!
73, K7TRK
-----Original Message----- From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of John Geiger Sent: Tuesday, January 1, 2019 6:43 PM To: Douglas Quagliana Cc: Douglas B Tabor; AMSAT -BB Subject: Re: [amsat-bb] Arrow modification
Cushcraft, MFJ, Hy-Gain, and Jetstream all make dualband yagis with both bands having the same polarization. Cushcraft is a little unique in that the elements for one band are on the top of the boom, and the elements for the other band are on the bottom side of the boom. Both bands have driven elements that are coax fed and there is a coax harness with a T connector and short runs of RG-58 which does to the feedpoint for each driven element.
The other brands use elements that go through the boom, and they are interspaced with each other on the boom. I know Jetstream only has the coax attached to the 2 meter driven element, and I think it couples to the 70cm driven element through their harmonic relationship. I think Hy-Gain and MFJ do the same thing, but I am not positive on those, as I haven't looked at their manuals recently.
I have the Cushcraft A270-10s which has 5 elements on each band on a 6 foot boom. I have the 2 meter elements on the bottom side of the boom, and the 70cm elements on the top of the boom. The band which is on the bottom of the boom seems to have a pretty normal pattern. The band which is on the top of the boom seems to have its pattern skewed where the main elevation lobes are at a pretty high angle. On Mode J satellites I don't hear the satellite very well unless it is a rather high pass, and I don't hear it well during the beginning or end of the pass. SO50 is rather hard to hear at all, AO51, AO27, and FO29 are/were easier to hear, but it still shows the same type of pattern, you don't hear much until you get above 25 to 30 degrees of elevation. The Mode B satellites exhibit a much more normal pattern-I can hear the XW2 and CAS-4 satellites throughout most of the pass, and AO91 and AO92 through most of the pass also, with some fading here and there when the satellite changes polarization.
I have also owned the Jetstream dualband yagi in the past and it had pretty impressive performance for an antenna with a 2 1/2 foot boom. Its elevation pattern seemed to be more normal than what I get with the Cushcraft on 70cm. The biggest problem with the Jetstream right now is finding one. R and L electronics is out of them, Jetstream is out of them, RW antennas on ebay is out of them also. I bought a used one on ebay and when it arrived it was the Jetstream dualband vertical instead. They luckily refunded my money, but they didn't have the used yagi to send me instead. They seem pretty scarce right now, but they did perform pretty well on the satellites.
I have not used the MFJ or Hy-Gain yagis so I cannot comment on them. The MFJ yagi with the 4 elements on 2 meters and 7 elements on 70cm uses a circuit board for the feedpoint. That looked a little too fragile to me for the long term. MFJ has a newer yagi with 3 elements on 2m and 5 elements on 70cm with a different feedpoint arrangement. I think it is pretty much a direct copy of the Hy-Gain dualband yagi, since both companies are owned by MFJ. I cannot comment on the radiation patterns of these antennas, but they could be similar to the Jetstream since the elements go through the boom like they do on the Jetstream.
If we had many more satellites running Mode J I would replace the Cushcraft with one of these others. Right now with only 2 satellites using Mode J, and FO29 still pretty workable, I haven't bothered as I am also into 2 meter SSB and the Cushcraft is twice as long as the others in terms of boom length so it is probably a better performer on that band. It also seems a little more rugged than the others. The Jetstream is limited to 100 watts and I blew out one of the driven element arrangements on 2m running 80-90 watts through it. It was under warranty so Jetstream sent me a new driven element, but I still had to go up on the roof and replace it, something that might be hard to do depending on one's setup.
For a portable hand held yagi I think the Jetstream would work very nicely. It is light, doesn't need a duplexer, will handle 50 watts from a FT100/FT857/FT991/FT897/Icom 706MKIIG type of radio, and the elements are attached with wingnuts which can be broken down very easily for transport.
73 John AF5CC
On Tue, Jan 1, 2019 at 7:53 PM Douglas Quagliana dquagliana@gmail.com wrote:
I'm not sure if anyone has modified an Arrow to put the elements in the same plane.
However, Kent's "cheap LEO" yagi puts the 2m and 70cm elements all in the same plane, so it can be done (if you know what you are doing.) See
http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf
73, Douglas KA2UPW/5
On Dec 31, 2018, at 9:37 PM, Kenneth P Alexander ve3hls@gmail.com
wrote:
Hi Doug,
Simply moving them into the same plane will likely cause problems because the bands are harmonically related. The 2m elements will make a mess of the 70cm radiation pattern if they're in the same plane. That said, I
did
just stumble across a satellite yagi design where the elements were intentionally in the same plane. Only the 2m yagi is fed and a passive
70
cm driven element is placed close to the 2m driven element so the 2m element excites the 70 cm passive element, causing it to radiate on 70
cm.
I believe it's called an open sleeve design. I think it was 3 elements
on
2m and 3 or 4 elements on 70 cm. Sorry I didn't bookmark the page. I don't remember where I saw it. Hopefully someone else saw it and
remembers.
Happy New Year,
Ken bueng-ken.com
On Tue, Jan 1, 2019 at 10:20 AM Douglas B Tabor via AMSAT-BB < amsat-bb@amsat.org> wrote:
I’ve been using my well faded Arrow for 4 years. The boom is a much appreciated LIDstick so the old man can swing it as well as a 3 year
old.
Has anyone modified the Arrow to have 2m and 70cm elements in the same plane (instead of stock 90 degrees)? I’m just curious what the
performance
result might be - I know it would be easier to get in and out of the RoverMobile instead of doing the twist-and-angle it out.
HNY and 73,
Doug, N6UA
Douglas Tabor dtabor52@icloud.com
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions
expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions expressed
are solely those of the author, and do not reflect the official views of
AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb