SDL Militiry Air Lpda Antenna

[captkel]

If you haven't heard, I GOT ONE yesterday and put it up today. Also if you haven't heard, I have been experimenting with a modified Military Air collinear antenna (formerly a 2 meter collinear). Now I have something to compare the collinear's performance to. Both antennas where mounted 30' up, feeding through a Par 225-400 Mhz band pass filter, This next part is only temporary...feeding to a Radio Shack VHF/UHF 10db variable gain mast mounted pre amp that is set at maximum, and RG6 coax.
With the SDL Log antenna I'm still receiving the same ground transmissions as before however 2 of the frequencies are 1 bar in signal strength stronger The local time here is 2:30 PM. Usually I notice that the signal strengths increase between 5 and 8 PM local and before sunrise so I'll recheck then. I assume I assembled the SDL correctly...For me it was a no brainier. , I'm waiting for a quality pre amp designed for this band to arrive, I did receive 50' of LMR400 and the proper jumper cables to go between the filter and pre amp. By the way I did run, as a test, the LMR400 direct from the SDL antenna to my Radio and I could only hear one ground transmission, barely. I'm about 35 miles away from that transmitter. More reports to come

KEL

 

[zguy1243]

If you haven't heard, I GOT ONE yesterday and put it up today. Also if you haven't heard, I have been experimenting with a modified Military Air collinear antenna (formerly a 2 meter collinear). Now I have something to compare the collinear's performance to. Both antennas where mounted 30' up, feeding through a Par 225-400 Mhz band pass filter, This next part is only temporary...feeding to a Radio Shack VHF/UHF 10db variable gain mast mounted pre amp that is set at maximum, and RG6 coax.
With the SDL Log antenna I'm still receiving the same ground transmissions as before however 2 of the frequencies are 1 bar in signal strength stronger The local time here is 2:30 PM. Usually I notice that the signal strengths increase between 5 and 8 PM local and before sunrise so I'll recheck then. I assume I assembled the SDL correctly...For me it was a no brainier. , I'm waiting for a quality pre amp designed for this band to arrive, I did receive 50' of LMR400 and the proper jumper cables to go between the filter and pre amp. By the way I did run, as a test, the LMR400 direct from the SDL antenna to my Radio and I could only hear one ground transmission, barely. I'm about 35 miles away from that transmitter. More reports to come

KEL

KEL,

Get me a closer pick of the antenna. It almost looks assembled wrong...Does your order look like this?

 

[zguy1243]

In your photo it appears all the elements go straight up each boom and don't stagger like they should. The antenna will not perform very well if it is in fact wrong like I think it is...


Edit,

I just downloaded and zoomed in on that pic. It is assembled wrong thus your performance not nearly at its peak. I PM'd you my cell number. Call me if you need some explanation.

 

[zguy1243]

see element numbers,

 

[captkel]

How about now

 

[zguy1243]

How about now

Spot on. Now give it a try

 

[captkel]

After assembling it correctly the signals shot up 2 bars and we now have full quieting .It's amazing that it will work somewhat if done wrong. I swung the antenna down toward Miami and I can hear an RCAG frequency that I could not even get a peep out of before, it has intermittent full quieting. I think we got it...OK now I'm impressed The collinear will be reworked for sure. I'll change it to a VHF air band antenna. When it was a 2 meter antenna it worked OK until I discovered the corner reflector. Thanks Again for all your help!! Your AWSOME...and the SDL too!

P.S. You gotta make one of these for VHF, I can handle one up to 20' long

KEL

 

[zguy1243]

After assembling it correctly the signals shot up 2 bars and we now have full quieting .It's amazing that it will work somewhat if done wrong. I swung the antenna down toward Miami and I can hear an RCAG frequency that I could not even get a peep out of before, it has intermittent full quieting. I think we got it...OK now I'm impressed The collinear will be reworked for sure. I'll change it to a VHF air band antenna. When it was a 2 meter antenna it worked OK until I discovered the corner reflector. Thanks Again for all your help!! Your AWSOME...and the SDL too!

P.S. You gotta make one of these for VHF, I can handle one up to 20' long

KEL

Glad to hear your are liking it. Now you have another band that will open up all kinds of opportunities for DX and interesting comms. The UHF band is a very active place when you have the right gear to hear it. A good rotor is almost a necessity with the SDL. It is very directional. I use a Yaesu G-450A with mine. Keep us updated on what you catch now. When you get your good preamp in and a filter with it up there things will really pick up again. Those high gain TV amps have a very nasty noise figure. Prcguy is spot on with his comments on the angle linear amplifier. I also just picked up 4 New York Microwave 225-400Mhz bandpass filters on Ebay. I paid 20 dollars each for these. These units have the lowest insertion loss of any filter I have ever tried. They really do the job. I don't need all the filters, if you want one I will send you one down when they come in. I am currently using this filter on my omni before the angle linear high level amp. Also send me a nice photo of the antenna installed if you don't mind. I like to post photos of the antennas that customers install on the website. I just received some very cool photos from a certain defense contractor that bought a few SDL's that will be up soon. Very cool stuff..

 

[captkel]

Glad to hear your are liking it. Now you have another band that will open up all kinds of opportunities for DX and interesting comms. The UHF band is a very active place when you have the right gear to hear it. A good rotor is almost a necessity with the SDL. It is very directional. I use a Yaesu G-450A with mine. Keep us updated on what you catch now. When you get your good preamp in and a filter with it up there things will really pick up again. Those high gain TV amps have a very nasty noise figure. Prcguy is spot on with his comments on the angle linear amplifier. I also just picked up 4 New York Microwave 225-400Mhz bandpass filters on Ebay. I paid 20 dollars each for these. These units have the lowest insertion loss of any filter I have ever tried. They really do the job. I don't need all the filters, if you want one I will send you one down when they come in. I am currently using this filter on my omni before the angle linear high level amp. Also send me a nice photo of the antenna installed if you don't mind. I like to post photos of the antennas that customers install on the website. I just received some very cool photos from a certain defense contractor that bought a few SDL's that will be up soon. Very cool stuff..

I've got the PAR UHF band pass filter up there now, however I would love to try the New York one. I did a quick search for them on the internet one day and couldn't find them and then I forgot all about it...I probably got busy at work. I'm having fun this morning logging ARTCC freqs. Here's some pictures including one of my VHF setup that got damaged in a bad storm last week. I will be repairing that this morning, just waiting for help to arrive. I've been trying to upload some more pictures but it's not working.
I'll send them on Facebook.
I figured out how to do the smilie

Catch you later

KEL

 

[CalebATC]

Whats the pipe with the caps for? Preamp or filter I am guessing?

Nice setup. Can't wait to get one of these babies. I'd like to see one of those pictures of the military contractors also.

 

[captkel]

Whats the pipe with the caps for? Preamp or filter I am guessing?

You guessed it. In the other picture the top antenna (corner reflector) on the bent mast was working just fine pointing at the ground but I needed to repair the mast and the broken (snapped in two) quagi antenna. As I was lowering the mast the bend got worse, I thought I had it repaired but on the way up the mast bent again and the repaired antenna broke in a different spot so I brought it all down to the ground and went out to dinner. I know I'm asking way to much from the pipe and antenna and it shows. Still pondering which way to go now
I'll sleep on it.
KEL

 

[CalebATC]

Oh, you should see the iron pipe that came with this tower. Weighs about 40 pounds!!! 8 foot tall, so went to Home Depot and got 12' tall metal pipe that was much lighter, taller, and shiny! 2" wide, works great.

Just get a new one. I'm sure those antennas weigh quite a bit; might wanna go for a bigger pipe!!!

 

[captkel]

Oh, you should see the iron pipe that came with this tower. Weighs about 40 pounds!!! 8 foot tall, so went to Home Depot and got 12' tall metal pipe that was much lighter, taller, and shiny! 2" wide, works great.

Just get a new one. I'm sure those antennas weigh quite a bit; might wanna go for a bigger pipe!!!

Sounds like you bought Electrical metallic tubing, or EMT. It is more commonly known as conduit. It is made from high-grade rolled steel, The outside surface is coated with clear zinc chromate, that's why it's shinny. The interior is zinc-coated. These coatings help prevent corrosion in outdoor installations. EMT is easily cut and bent so it won't handle much weight if any at all. Mine is made out of Iron pipe and it looks just like this except I painted it green... and it's longer...hehe Tilt-Over Mast - The RadioReference Wiki Iron pipe bends too as I soon found out after building it. My antennas a very light weight however when there on the end of the pipe they can cause the opposite end of the pipe to bend or bow.
I invested a lot of time and money in it so I'd rather not junk it. It looks like I'll have to spend some more money on it... and I have. It's in the repair and reinforcement phase right now. It should be ready to go back up in about two weeks, I basically can only work on it on the weekends along with my other chores. Bigger diameter pipe would be heavier and the winch may not pick it up and it would still bend. One section-20' of the 1 1/2" pipe that is on it weighs about 60# and that's just one pipe out of several. The only repair I did so far was on the two 2" pipes cemented in the ground. They went from a straight 90 degree angle to sixty degrees. I straightened them out and reinforced them to prevent them from bending in the future. And now for some FUN news: I'm listing to all kinds of things on the UHF military band a little better tonight, I got the NEW pre amp in and hooked it up. It's working quite well. The farthest ground comms I can routinely get so far is the Homestead (HST) Air Reserve Base ATIS about 55 miles away. The signal was a S-1 now it's a S-3. The SDL antenna is currently aimed south of me towards Miami, It's doing a S-1 to S-2 off the back of the antenna on signals north of me...pretty cool. Those signals north of me went from a S-3 to now almost full scale

KEL

 

[CalebATC]

Yep that's it. Couldn't think of the name of it. That's why dad goes shopping!

This still does just as good, and has no bend in it after some gust of 50 MPH we had!