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kc4umo
02-03-2008, 09:08 PM
Spent the week end working on a new 70cm CP yagi.
This is for working sats.
I always had a good 2 meter atenna but never a good 70 cm.
Not a lot on the internet on building one either.

This is a 10 X 10 RHCP yagi.
Designed by me.
One set of elements are shifted 1/4 wave legnth ahead of the other. Fed with two 75 ohm 1/4 wave legnth coax splitters.

Here is the link for the whole assemply and fabrication process:
http://www.gokarters.com/vbforum/showth ... #post14986 (http://www.gokarters.com/vbforum/showthread.php?p=14986#post14986)

I have not finished testing but I tell you it works great.
I had a chance to work both A)-51 and VO-52 a few moments ago.
Both was on a low short pass. This makes it more difficult because of trees.
51 uses 70 cm down and 52 uses 70 cm up.
That was a great test.
10 watts and no preamp..

Me is happy.
Got about 20 bucks in this antenna.

http://www.gokarters.com/vbforum/attachment.php?attachmentid=592&stc=1&d=1202085329
M0GLO
02-03-2008, 09:32 PM
Sweet!
N5RLR
02-04-2008, 12:08 AM
Excellent. :mrgreen: Yeah, shifting one set of elements λ/4 ahead makes for an easier feed than monkeying with a 270º, 93(?)Ω delay line [so my research tells me].

It may be too early in your testing to tell, but I wonder how it'll be with cross-polarization [RHCP vs. LHCP].

In all, fine work. 8)
kc4umo
02-04-2008, 06:52 AM
Excellent. :mrgreen: Yeah, shifting one set of elements λ/4 ahead makes for an easier feed than monkeying with a 270º, 93(?)Ω delay line [so my research tells me].

It may be too early in your testing to tell, but I wonder how it'll be with cross-polarization [RHCP vs. LHCP].

In all, fine work. 8)

Still working on the polarization.
With the set of elements 1/4 wave ahead it is (to my understanging) electrically RHCP.
But dont quote me yet.
02-04-2008, 11:43 AM
She's a beauty. That is really nice.
02-04-2008, 11:48 AM
What about the phasing? How do you connect the two driven elements at once and phase them properly?
kc4umo
02-04-2008, 03:48 PM
Thanks for the comments guy's.

N9XR,
Since the aqntenna uses gamma match feed and one set of elements is advanced 1/4 wave ahead, it was fairly easy. I used two pieces of RG-59, (the underground stuff with the heavy braid).
These are cut 1/4 wave legnth also. There is no tee in line. Both phasing cables connect to a female N-type chassis connector, and water proofing was added.
N3ATS
02-06-2008, 07:35 PM
Very nice job! How did you fasten the elements through the boom?
kc4umo
02-07-2008, 07:19 AM
Good question.
As you can see in the next few pics, when the plastic anchor id pushed through the boom, it is very tight. When you insert the element (and takes a little force) the plastic expands and makes a very tight fit. I put just a dab of hot glue on them to seat it a bit. But is not needed.


http://www.gokarters.com/vbforum/attachment.php?attachmentid=576&stc=1&d=1202049830

http://www.gokarters.com/vbforum/attachment.php?attachmentid=583&stc=1&d=1202083650
w2amr
02-12-2009, 03:55 PM
Very nice work
N8YX
03-21-2009, 03:34 PM
Good job. Now who's on the birds these days? My -726R needs some extraterrestrial motivation...
kc4umo
08-10-2009, 10:04 AM
Good job. Now who's on the birds these days? My -726R needs some extraterrestrial motivation...

Not sure how I missed this reply! :wall:

The birds are very active . AO-7 is great still. Be sure to listen for K3SZH. He holds the most contacts on the AO-7 Log.

I tend to stay away from the FM birds. Not much into competition.
N8YX
08-10-2009, 10:10 AM
As I told you via PM a while back, I picked another of those rigs up. This one with the satellite module, too.

It's currently set up as HF/2/440 but I can swap a spare 430 module into it for sat work.

Just need to figure out an antenna arrangement...
kc4umo
08-10-2009, 11:34 AM
For the FM birds a couple of turn styles would work fine. I have even used verticals on AO-51 with fair results. I have tried the egg beaters and were not impressed with them. The birds have to be at 30 degree of higher due to radiated pattern.

A 3 element VHF with 4 element UHF mounted on a wooded pole works quite nice. I built a few like that. One good one was a dual quagi design. Worked very well. Light weight.

But working AO-7 ssb is a different story. You need a good UHF ant with some gain. I only run a couple of watts with my current setup.

That would be a nice treat with the lastest 726 you picked up.
N8YX
08-10-2009, 11:56 AM
What are you using for an elevation rotor, Buddy?
kc4umo
08-10-2009, 01:47 PM
What are you using for an elevation rotor, Buddy?

I use a Radio shack rotor for azimuth. I made a bracket to hold an Alliance U100 sideways directly over top of the RS rotor. I picked up an old 30mhz antenna 20 years ago and that is my cross boom to hold both antennas.

Here is a distant pick of the setup. I will take a close up pick of the bracket later.

I am working on a new project now. I want to get back into EME so I want to build a new asimuth / elevation setup. The asimuch will be gear driven and the elevation will use a jack like you found on the old c-band dishes.
N8YX
08-10-2009, 02:00 PM
IF (and this is a big "if") I still have my old R/S rotor around I was planning on doing similar.

2M switchable polarity Yagi on one side; 430 and 1.2 GHz on the other. Thoughts are to put it up on 30ft of Rohn 25 at the side of my house and use a standoff on the tower as a support point for a wire antenna which now traverses the area.
kc4umo
08-10-2009, 02:31 PM
That will work.
Wished I had something for 1.2. One day I guess.
Do you have the Alliance rotor?

If so, there is a mod that should be done to it. Helps a lot. There is a gear in it the has one notch sticking up. It is what clicks the signal back to the control box. zThe mod is to add another notch across from the original on the other side. This makes the "click" happen twice. And when the HEO sats are back, this will be needed.
N8YX
08-10-2009, 02:34 PM
That will work.
Wished I had something for 1.2. One day I guess.
Do you have the Alliance rotor?

If so, there is a mod that should be done to it. Helps a lot. There is a gear in it the has one notch sticking up. It is what clicks the signal back to the control box. zThe mod is to add another notch across from the original on the other side. This makes the "click" happen twice. And when the HEO sats are back, this will be needed.
The HD73, perhaps?

No....not yet...but thanks for the info. I'll have to mod it when I get one.

Nothing for 1.2 (or 220 SSB/CW) at the moment but I'm working on that. One or more of the 726r setups will be used as IFs for some transverters and I'll probably throw in 902 for good measure.
kc4umo
08-10-2009, 02:48 PM
The HD73 makes a decent asimuth rotor. Bu you will need the U100 for elevation.
Since it has a through hole and can be mounted with antennas on both sides for balance. I still find them all the time on top of houses in the city. All you have to do is stop and tell them that you would be more that glad to take that eye sore off the roof for them.

I need to look at prices on the transverters. I may use one of my 726's for the IF also.