The AM Forum
July 23, 2024, 05:41:13 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: An Opinion on Open Wire for 6M use - From a Pro  (Read 10336 times)
0 Members and 1 Guest are viewing this topic.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« on: February 09, 2005, 01:26:52 PM »

There was a sub-thread going here about using openwire vs: hardline on 6M to reduce losses.  I axed a coupla of well known VHF/UHF friends their opinions on this.  One friend, Steve, K1FO is well known for his years of VHF/UHF moonbounce, ham line of antennas, and amplifier construction and company.  I've posted his response below (with his permission) regarding using open wire for a 600' run.... I also have another question in to him regarding the loss of using a PVC jacket on the openwire - awaiting response.
T
--------------
FROM STEVE, K1FO:

A couple comments Tom.

Yes I am using open wire phasing lines on my 432 array.
The open wire is made from #8 enameled wire spaced .35" which makes
200 ohm line.  It is not affected by rain.  Ice is another story, but it
doesn't matter since the Yagis themselves are useless with ice on them.

I would advise against 3" spacing and bare copper.
Bare copper will oxidize and greatly increase losses.  You should go
with double enameled wire.  Useful life in our climate will be about 10 years before the enamel will be gone from UV and errosion.

3" spacing is too far apart.  I estimate it to be 460 ohms, which will be
affected by rain and things near the line.  I would recommend a maximum of 300 ohm line which would be about 3/4" spacing with #10 wire.  I also recommend Teflon spacers.  Teflon is ultraviolet tolerant and low loss.

However losses willstill be significant with a 600' run. The best I was able
to measure on a 50' section of my 200 ohm line was that at 432 losses were similar to 7/8" Andrew LDF  (LDF5-50).  Which makes the open wire line well worth it for phasing lines, but if questionable value for transmission line especially when the loss of open wire to coax matching sections are included.

I can't find the reference right now, but somewhere I did find how to calculate the loss of open wire line.  If I remember right the calculated losses were lower  than my measured losses, but the 2 numbers were in the ballpark. Calculated  maybe something like 20% lower than measured, but I can't exactly remember.

If it were me, I would go with 1-5/8  or 1-1/4" Andrew LDF.  There are incredible quantities of this cable in the surplus market and you can usually by 1-5/8" LDF  surplus for less than you can buy 7/8 cable.  Loss of 600' will be only .64 dB  which I'm sure is lower than you will be able to do with open wire.  Plus you don't  have the problem of supporting the 600' run of open wire line.   I have seen 500' rolls of 1-5/8 sell for under $1,000.

Steve,  K1FO

-------------

Tom,

Yes you can post my response.

3/4" aluminum jacket coax should be about 0.4 dB loss / 100' @ 50 MHz, your 0.5 dB measurement is in the ballpark.

Low density foam copper jacket is significantly lower loss for the same size.  Even LDF5-50, Andrew 7/8" is only 0.26 dB / 100' at 50 MHz.  But again, you will most likely find that 1-1/4" and 1-5/8" will sell for less than 7/8" surplus as most hams are afraid of the real big coax.

Steve

----------------



My Intitial eMail to Steve:

Hi Steve,

I'm not sure if you remember me, but I stopped by your QTH back in 1974 with   Bob, N1KW and took a look at your moonbounce station. I remember some HB  8877 amplifiers and a nice antenna H frame built from Hatry's tower parts...     :-)

Anyway, I am designing up a big H frame for 6M using four, homebrew, 48'   boom Yagis. Three of the Yagis are already built and working on the tower as  a temporary stack at 110', 80' and 50' with a Stackmatch.

        Here's a picture:

    http://home.comcast.net/~k1jj/wsb/media/254120/site1062.jpg


I understand that you used open line for interconnecting one of your UHF
Yagi arrays.


Here's the problem:


The feedline run to the tower is about 600'.  The loss is too high for me
even using hardline. I was considering using open wire for the run.


I  don't want to use a preamp or use a remote controlled 8877 amplifier at the tower to eliminate the TX/RX 3db loss from hardline

I planned on inter-connecting the Yagis with 50 ohm hardline, (having a
180/0 switch for top/ bottom high/low angle) and then tapping the openwire  with a balun at the 50 ohm point using a stub.

The 600' of openwire would then run back to the shack where a reverse tap would bring it back to 50 ohm coax.

I figured on maybe 3" open wire spreader spacing with #10 bare wire.


What's you opinion on doing this? Is 3" spacing too much and how much does  the WX affect yours?

Any suggestions will be much appreciated before I proceed.

       73,
        Tom, K1JJ
        Marlborough, CT
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
WA1GFZ
Member

Offline Offline

Posts: 11151



« Reply #1 on: February 09, 2005, 01:36:53 PM »

Hey Tom,
I wonder if the maggot has a stash of 7/8 hardline??
Heck I even have a 130 foot hunk. This is a lot more common
in 2 way land. All the trunking sites that went down must have
provided a lot of used stuff around. I have never seen the bigger stuff used around here except commerical radio and TV. I may have some spare connectors kicking around.
Sounds like you need to give big Al a call.
Logged
KL7OF
Member

Offline Offline

Posts: 2311



« Reply #2 on: February 09, 2005, 04:02:54 PM »

Tom those 6 meter Yagis are way cool.....  How do they rotate?.... We must have worked on 6M in the past....This was my 3rd cycle on 6....and the 2 before this one I was very gung ho and whirlwide......Have you had other calls?   Steve
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« Reply #3 on: February 09, 2005, 05:29:47 PM »

Quote from: KL7OF
Tom those 6 meter Yagis are way cool.....  How do they rotate?.... We must have worked on 6M in the past....This was my 3rd cycle on 6....and the 2 before this one I was very gung ho and whirlwide......Have you had other calls?   Steve


Hi Steve,

They are rotated for now by the Armstrong method. Look closely and you will see a rope attached to each gate.  Homebrew Yagis and gates that move 330 degrees around the tower. Didn't want to spring for rotators until I was sure, and glad I didn't now. They can be pointed in different directions and switched individually or run all the same way in phase.  But they are best for long haul F2 and there is none on 6M now. My mistake.  So gonna put them into an H frame, make a forth one, lower height on
the tower and switchable for hi/low angle to cover both E skip and tropo stuff I'm hoping.

Good on your 3 cycles there! Wonder what you used for ants/ rigs. You haven't heard me on cuz this is my first 6M effort just last 6 months.  With the cycle headed down, what timing, huh?   :lol:


Frank - yep, Big al and the Maggot will be the guys to call for sure. I'm thinking seriously of going the BIG hardline route as Steve/K1FO suggests IF I can get it real cheap.

BTW, Al told me that a tractor ran over the Maggot's hardline stash a year ago- ruined 1000's of feet. He was ripped.  But he probably got a lot more since, knowing him...

T
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
KL7OF
Member

Offline Offline

Posts: 2311



« Reply #4 on: February 09, 2005, 06:31:59 PM »

Quote K1JJ......[Good on your 3 cycles there! Wonder what you used for ants/ rigs. You haven't heard me on cuz this is my first 6M effort just last 6 months.  With the cycle headed down, what timing, huh?   :lol:

Tom...First I used a barefoot Swan 250 and a 4 ele yagi @60 ft  Then I moved up to a 6 el long boom (42ft) homebrew and later added a homebrew pr 3-500's...My first cycle on 6 was terrific...You could work the world on 6 with 10 watts....The band was open every day for a couple years,,,The next cycle was very good but not as good and I built the long boom yagi and raised it to 80 ft..Then I built the leeyar......This last cycle I used the swan some and got an Icom 551D and a 600watt brick.....Not nearly as much excitement as the two cycles before....I don't even have the 6 meter antenna hooked up right now...The old long boomer is in a pine tree @60 ft now.....I haven't turned it in over a year....I guess I am spoiled by the great condx in the old days....Hang in there...With that 4 yagi H setup, you can make your own condx....  gud luk....Steve
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« Reply #5 on: February 09, 2005, 07:06:52 PM »

Hi Steve,

Wow, looks like you're really into 6M there.   That's a real LONG boom Yagi at 42' and 6els....

I'm always amazed how many Amers are into 6M. Some are real serious about it.

What I like about the band is that condix are always surprising and random at best.  And getting a real effective antenna system is within the realm of most guys.

Catch ya on 75M west soon, OM.

T
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
KL7OF
Member

Offline Offline

Posts: 2311



« Reply #6 on: February 09, 2005, 08:56:26 PM »

You are right Tom.......in that there is excitement in the E openings and the the tropo stuff...I used to have 2 scanners running to watch the MUF climb .....Speakers in the shop and outside speakers to alert me ...rigs at the ready....Very serious........No web information to predict Tropo like we have now.....But I made quite a few tropos during the season..fun stuff..
Logged
Art
Guest
« Reply #7 on: February 10, 2005, 08:52:26 AM »

'seems to me a good quality TV twinlead would do the job nicely for low power. . . .

-ap
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.067 seconds with 19 queries.