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Scanner / Receiver Antennas For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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Old 12-31-2006, 7:36 PM
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Default 6 meter loop dipole.

Here is one of the latest creations from the basement. Took the idea of a halfwave loop or what some call HALO. All the plans I have seen use a gamma match to feed this antenna. I decided to use a T match. It's been a bit tricky and there has been some copper put back in the heap to use for a higher frequency. I think Im getting close though. You'll see a few zip ties in there, those aren't as build. Plan on testing it tomorrow with the analyzer.





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Old 12-31-2006, 7:47 PM
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very awesome. horizontal polarization?
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Old 12-31-2006, 7:52 PM
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Seems to me that back about the early 60's there was an antenna design
like this that was on the market by I think Cush Craft. May have the
company wrong, but I did use one on 6 meters back then. They worked
fairly well in those days when most of the activity was of the horizontal polarity.

The antenna back then had 3 loops that went all the way around. They
used a pair of large discs that were used for tuning the antenna. Had
a threaded screw on one disc that you moved closer or further away
from the fixed disc. When you got the SWR as low as you could, you
would lock the rotating disc with a lock nut.

Today most of the 6 meter mobile activity is on FM and uses verticle
polorized antennas.

Jim



[QUOTE=KC8JPZ]Here is one of the latest creations from the basement.
Took the idea of a halfwave loop or what some call HALO.
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Old 12-31-2006, 8:26 PM
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Yes Jonny, it is horizontal and thank you.

Jim,I'm not focusing on FM as much as I am SSB. My intention is to use the antenna mobile in the Sweepstakes in Jan.
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Old 12-31-2006, 10:13 PM
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Well, I managed to finish up tonight with the test ready version. Took it outside and put it up on the test mast and began the process ( my favorite part ). I think I got pretty lucky. Tuned the T match with the shorting straps to acheive best SWR, It reached best the first time at about 49.5 mhz. Took the tubing cutter and trimmed off about 1 centimeter from each side of the opening of the loop at a time. After a total of 6 centimeters removed I managed to bring up resonance to 50.100 mhz. with a SWR reading of less than 1.2:1. I think I may still be able to drop it a bit with the T match adjustment. I plan on wrighting up the plans for this loop soon, probably after the contest or all antennas are finalized.
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Old 01-04-2007, 1:09 PM
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Quote:
Originally Posted by jim202
Seems to me that back about the early 60's there was an antenna design
like this that was on the market by I think Cush Craft. May have the
company wrong, but I did use one on 6 meters back then. They worked
fairly well in those days when most of the activity was of the horizontal polarity.

The antenna back then had 3 loops that went all the way around. They
used a pair of large discs that were used for tuning the antenna. Had
a threaded screw on one disc that you moved closer or further away
from the fixed disc. When you got the SWR as low as you could, you
would lock the rotating disc with a lock nut.

Today most of the 6 meter mobile activity is on FM and uses verticle
polorized antennas.

Jim

Here was my dad's old 6 meter halo which is what you described. (Yes, that is me in 1966 standing by the car.)
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Old 01-04-2007, 2:38 PM
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I love those old pics and nice job with the antenna. Will look for 'ya in January (okay, it's 337 miles between us, but you never know!).

There is one 6m FM repeater in town here and I have NEVER heard anyone on it, although I have had fun working folks in the SE US when the band is open.

John K9RZZ
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Old 01-04-2007, 4:31 PM
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Thanks for sharing the pictures, I love seeing pics from the Elmers. Thats an interesting design, the first I've seen of those. Seems to make sense. Smaller loop but more material there.

K9RZZ John, get those amps warmed up. We will be running a few hundred watts ourselves. I'd like to make it up to the north west and activate EN71. If time permits I will. We will be on 6 meters, 2 meters, 70cm and possibly 220. I'm pretty sure the majority of time we will be on SSB.

I heard a few guys on our big machine here in Columbus today talking about the 6meter machine they are working on. Sounds like they may have it up and running here before too long.

Listen For W8OSP/Rover, Were gonna learn the ropes of rover contesting on his call Hi
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Old 01-05-2007, 3:42 PM
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Quote:
Originally Posted by KC8JPZ
Yes Jonny, it is horizontal and thank you.

Jim,I'm not focusing on FM as much as I am SSB. My intention is to use the antenna mobile in the Sweepstakes in Jan.
Hope to work you during the Sweepstakes! I'll be on 6 with the FT817 and my homebrew 2 element 6 meter yagi. operating up in the hills of Colorado. I'll be in Grid Square DN70.
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Old 01-05-2007, 3:43 PM
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I will be on 6 meters,2 meters, and 432 MHz
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Old 01-06-2007, 12:38 PM
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Mobile Test.

Seems to be working great around town here so far. Talking to a couple guys I know within about 20 miles on 20 watts is no problem. Would have been nice to get an opening.

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Old 01-06-2007, 1:00 PM
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wow that sure is interesting! Wish I could build things like that, but I lack the knowledge in that area.

Have you ever though what people think it is when driving around?
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Old 01-06-2007, 1:24 PM
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Thanks kicktd, look around for plans. There is all kinds of fun stuff to build. Tons of info on building antennas too. You do get some weird looks from just about everyone you pass with this stuck on the bumper. Lots of questions at the gas station too.
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Old 01-06-2007, 1:34 PM
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Tell them it's a new basketball training device. They have to run, dribble, and shoot, while you drive around real slow.
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Old 01-06-2007, 1:50 PM
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Real slow?
Heres a couple more.

I have it all taken apart again for painting.


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Old 01-06-2007, 5:58 PM
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How did you bend the copper tubes?
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Old 01-06-2007, 6:02 PM
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N467RX, For this antenna I used the basement floor and drew a 36" circle on the concrete. This copper comes in a roll, so I rolled it out carefully on the floor shaping it at the same time. The stuff is really easy to work with. Just expensive. They call it a few different things I guess, but really its just a soft copper tubing from any hardware store.
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Old 01-06-2007, 10:28 PM
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What about the thickness of the tube? what bands can you hear with it?
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Old 01-07-2007, 3:27 AM
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Hi JPZ and all,

First of all there's no such thing as a "loop dipole", it's one or the other. What you have is a T matched halo plain and simple. I'll fill in the blank for the benefit of the readers, it's a dipole bent into a circle. It has roughly 0.8 unity gain, that is somewhat less than a straight dipole. That's because the figure 8 polar pattern of a dipole is bent into a circle which contracts it a bit. That design is a favorite of contest rovers, it can be deployed quickly but I wouldn't recommend driving around with it for pretty obvious reasons.

Kokomo, that's where your dad's Cushcraft Saturn Six came in being considerably smaller due to it's capacitively end loaded design. That's what those discs were for, they form a variable capacitor. The rings were connected in parallel effectively increasing the radiator's diameter and subsequently the SWR bandwidth. Those were the days before FM when AM was king, about the time that Hallicrafters produced a neat (not so) little 15W crystal controlled transceiver also marketed under the Lafayette name. They also produced identical looking 2M and CB rigs, that one was the CD-5A.

Most of those commercially made halos have disappeared, I used to have a single ring. FM using vertical polarization is the most popular mobile mode now but there are still some horizontals made for SSB such as the Squalo, a square halo made by M2 if I'm not mistaken. They're often stacked for 6M, 2M and 70cM.

With any luck I'll have my gamma fed rigid dipole fixed and the stacked 2M halos up in time for the 'test, if the band happens to open we'll have a blast!
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Old 01-07-2007, 7:35 AM
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Ok Warren, thanks for clearing that up. I've been having a hard time trying to figure out what it's called for sure. I was told that the original "halos" were complete circles and did not have a break. I don't know how that would work but, ok. I didn't want to call it a loop as to confuse anyone that it is a full lambda loop.

Anyhow, would you think the full halfwave would have an advantage over the more compact version like the saturn? I'm sure the shortened halos would be much easier to handle than what I have built. What about capture area? Think theres that much of a difference?

One more thing, why would you prefer the gamma over a T?
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Last edited by KC8JPZ; 01-07-2007 at 7:39 AM..
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