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SMF - Just Installed!

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 21 
 on: August 12, 2013, 11:26:02 AM 
Started by KE7TRP - Last post by KE7TRP
My latest antenna project is a DX engineering 10K+ 1 to 1 Current balun with wires for 40 and 80 meters. I am very pleased with the performance of the antenna so far. I would like to increase the bandwidth of 80.  I might try larger size wire to see if that helps.  I am currently using 14AWG wire.


The data was captured from the AIM4170C.  I wasted a week of testing and tuning the 80 meter antenna because the MFJ259B was reporting a 1.9 to 1 SWR for this antenna.  After noticing that the radio was showing 1.2 to 1, I asked my friend to bring his AIM over. 

The first file is the data for the 40 meter band.

The second two files are the same antenna on 80 meters.  One file is for 100Ft of feedline. The other plot is with another 100Ft of feedline added in for a total of 200Ft.


The setup:

55ft crank up tower up about 45 ft.
DX ENG 10K+ 1 to 1 current balun mounted on horizontal fiberglass arm
Two wires for 40 and two for 80 spead out 45 degrees forming a bow tie.



 22 
 on: August 12, 2013, 07:06:01 AM 
Started by AE7IX - Last post by N9DIX
Thanks C, I still don't have the shack finished so I'm not on the air yet. That's good to know about the caps and yes I'll have 220 available when I do get things going. I will have the case opened first and blow the cow-webs out and clean up the dust. Also will check the caps for any leaking. I was just worried that since it hasn't had any power applied for the past 18-20 years that the caps might of dried out. I'll let you know when I do get it running. Thanks again.
73's Jim

 23 
 on: August 10, 2013, 05:20:55 PM 
Started by KE7TRP - Last post by KE7TRP
Yes. Jim. That is an R390.  I had a Collins R390A and a R390.

C

 24 
 on: August 04, 2013, 01:05:36 PM 
Started by KE7TRP - Last post by KE7TRP
I have a problem with SWR on the 80 meter DBZ.  I had it tuned very flat.  I then installed it on a Fiberglass Arm of the top of the tower,  Now the minimum SWR is 1.8 to 1.  I swapped feedlines with no change.  I moved the legs around with little change. 

I had this same antenna and feedline pulled up the tower with rope and pulley to the same hight and the match was low. Now its high.  I have exhausted Ideas for now. 


 25 
 on: August 04, 2013, 08:17:48 AM 
Started by KE7TRP - Last post by KE7TRP
Yes. Over the last few years the noise in the neighborhood has increased to the point where I looked for another antenna.

I took the tower down yesterday.  I put the 40 DBZ north and sound one section down from the top.  The top holds the 80 DBZ east and west.    This way they are 10 ft apart and 90 degrees. 

One of us taped the beams coax to the second section when we taped up the coax for the 40DBZ. So when I cranked the tower up today, it ripped the coax connector out of the lead that runs to the Mosely beam.  ARRRGH!  I got the tower all cranked up, secured and ready to get on the air, had no RX on the beam, Walked outside and found the coax dangling 60 ft in the air. 

After I cool off, I will have to take the entire tower back down and repair it.
C

 26 
 on: August 03, 2013, 07:27:49 PM 
Started by KE7TRP - Last post by K3DAV
Low noise floor or higher noise floor.  Hmmm which one would I chose?  LOL

Most antennas of similar design do not make much difference, (if any) out beyond the curve of the Earth.  But the fact that there was a signal increase in the receive must also work in the opposite direction on xmit.  As little as the increase may be, it is only common sense that an antenna that receives better should transmit better.

But even if the difference is very small and nobody listening might even notice it, you have to admit that lower noise floor alone is worth all the effort.  That's the magic of DC grounding with a dipole.  Some of the local QRN goes to ground instead of your receiver.

 27 
 on: August 03, 2013, 12:09:13 PM 
Started by kg7ddl - Last post by KE7TRP
Its really a sad story.  Of course, Many believe that someone through him out the window. We will probably never know.

C

 28 
 on: August 03, 2013, 12:04:41 PM 
Started by KE7TRP - Last post by KE7TRP
I did some more testing.   I used glSDR application on my Android smart phone to access SDR receivers all over the world and US.   glSDR has a full band scope and water fall display.  I sent out a signal using my Call Sign on open frequencies and tuned the Remote receivers to match. In most cases the 40 DBZ is the same as the Open wire line doublet.  I don't see much difference , Sometimes there is a few DB higher on the DBZ. But for the most part it is a wash. I attempted to access each 360 degrees from my station. Since I am south west, This is difficult, However, I do not see any real difference broadside to end fire. I think this is because the antennas are pretty low on the nested tower.  I am really enjoying the significant decrease in noise with the DBZ and the lack of feedline radiation and interference over electronics.

 29 
 on: August 03, 2013, 12:04:26 PM 
Started by KE7TRP - Last post by KE7TRP
Yes. Performance is very close. This was a surprise as the open wire line antenna is a double on 40 and has some slight gain. 

I am really enjoying the lower noise floor and lack of noise.  The signals are slightly higher on RX and weak signal is far better.

The RG11 is much lighter coax and it Is 75 ohms and that really helps when you run full size coax like this from a weight standpoint.  When the weather cools off, I will try some RG8U and see if the bandwidth increases.  For me, I don't mine walking out to the yard and unfolding the ends of the antenna to work 80 meters.  It takes about 5 minutes and I take the golden retriever out back all the time anyways.

 30 
 on: August 02, 2013, 08:43:04 PM 
Started by KE7TRP - Last post by K3DAV
Clark, one of the reasons the 75 meter DBZ is not as broadbanded is because you used RG-11  75 ohm coax to make it.  75 and 160 meters are very picky with that kind of thing.  And if you used the RG-11 for the 40M DBZ, I am a little surprised that your SWR is that good, but then again 40 meters is not as picky.

Bazookas work best with regular basic RG-8 or RG-8X.  Bazookas love leaky coax.  Coax with tight shields do not perform as well,  And never use a coax with a foil lining around the foam insulator to make a Bazooka.  They still work but they are nowhere near as broadbanded.

It sounds like the 40M DBZ is going to work out very well.  Mainly you will notice weaker signals seem a bit cleaner because of the lower noise floor as your video shows clearly.  I watched your meter closely as you switched between antennas, and I think I saw a slightly higher signal on the Bazooka.  Not a big difference mind you, but that lower noise floor alone makes it worth it.  The choice of LMR-400 for feedline is a good idea.  That is the only coax I use these days.

Good goin' Clark.

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