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Author Topic: Remote HF Antenna Site / Can I feed ant. with 1,000ft of coax?  (Read 4990 times)
KG6SII
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« on: September 29, 2012, 08:47:23 PM »

Elmers,

My house (and wire dipole on the roof) are located half-way down the Eastern side of a 1,000 foot-tall hill.  Subsequently, 90% of my HF contacts are to the East.  I would like to make a change that should allow me to transmit better to the West.  My house is on 7 acres, and the top-most corner of my property nearly touches the ridge of the hill.  I am starting to do some portable mountain-topping on my property, but am working through the learning curve on portable antennas and power.  So far, my PSK31 waterfall is lighting up with tons of stations; something I have never seen before from the house.  So the location is good.  However I am sick of having to walk up the hill and operating there.

What are my options to remotely transceive with an antenna on the ridge line, and me in the comfort of my home?  Can I operate HF successfully with 1,000 feet of coax feeding my antenna?  If I install solar panels and batteries at the remote site, is there some kind of personal repeater that would allow me to receive and transmit wirelessly with the remote antenna site?

Thanks in advance,
Glenn KG6SII, General Class
Central Coast, CA
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WB4LCN
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« Reply #1 on: September 29, 2012, 09:23:02 PM »

Even with the best coax, you will have tremendous loses. A solar/battery control station may be possible. However, you'll have to have enough power for both the rig and the  control station.

dave Smiley
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First, make it work, then make it pretty.
Yaesu Rigs: Kenwood TS-480HX, FT-8900R, FTM-350AR (Bluetooth motorcycle mobile), VX-8DR, SB-102 boat anchor (built one as a kid)

Moderate Spock: "Live for a reasonable amount of time and scrape by."
K9ZMD
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Posts: 169




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« Reply #2 on: September 29, 2012, 11:14:26 PM »

Balanced line has substantially lower loss than coax, and is suitable for very long runs of transmission line.  To maintain the unbalanced 50 ohm (coax) entry to the house, as well as at the antenna feed point, you can use a balun at each end of the long balanced feed line.   Sort of like the following:

 (xcvr) ----coax ----[balun] ====== mucho mucho ladder line ======[balun] -----coax----(antenna)

See this site  http://www.dxengineering.com/search/department/antennas/part-type/baluns-ununs-and-chokes/product-line/dx-engineering-maxi-core-special-line-transformers?autoview=SKU for information about suitable baluns and a better description of their application.
Gary, K9ZMD/7
Ridgefield, WA
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KC4MOP
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Posts: 729




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« Reply #3 on: September 30, 2012, 04:40:40 AM »

A 1000 feet of anything is going to hurt.
You are on a good thought of using a repeater set up. That's the beauty of our Ham license. A low power 2M station between the house and the TX/RX site and your very own CTSS tone. The detection of that tone will assure privacy and can be used to for PTT of the remote TX.

A friend of mine used the same technology to be able to use 160M while he was mobile in his car while he traveled to work. His radio repeater was able to control his 'base station' and had the home station feel to his mobile rig, without running high power HF in the car and inefficient antennas while he's driving. There was no ability to QSY, though.

I email him and asked how it connected and I will copy-paste his response here.

If you are wanting to control other functions of the remote station, then it gets complicated with computers and the use of a spread spectrum modem to digitally take control of the remote station. I do not know what radio you are planning to use for the remote. Many modern rigs are capable of connection with the internet/home network. Solar power is another very good thought. Sounds like a great engineering challenge that you can do.
Here's a link to some ideas of remote control:
http://www.arrl.org/link-remote-control

Fred
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AC4RD
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« Reply #4 on: September 30, 2012, 04:45:58 AM »

Balanced line has substantially lower loss than coax, and is suitable for very long runs of transmission line. 

A "thumbs up" to Gary's answer!   In addition to the DX Engineering website's information about using window line for long transmission lines, you can always call DXE, tell them you're thinking about it, and get some input on their systems.  You can run very long runs of balanced line with very little loss--it's worth looking at!   73 GL!   --ken ac4rd
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KG4RUL
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« Reply #5 on: September 30, 2012, 05:12:54 AM »

Try this site to calculate some estimated loss numbers: http://www.vk1od.net/calc/tl/tllc.php
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K5LXP
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« Reply #6 on: September 30, 2012, 06:21:26 AM »

Wireless networking and a nominal power storage system will put a station right at the antenna.  Or 1000' of romex and an ethernet cable.  Seems a whole lot easier to do that than implement a very long transmission line setup.

Mark K5LXP
Albuquerque, NM
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W8JI
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« Reply #7 on: September 30, 2012, 06:43:19 AM »

The DX baluns are very good at HF. They are probably the best made around. But you need to be careful with loss. There are many places where people assume the ARRL loss specifications are correct. The ARRL loss data feeds into the mth that ladder line is like real air insulated open wire with thick copper conductors.

The ARRL grossly underestimates loss in ladder lines.

People here also are making statements that just are not true. It is easily possible to have less than 1 dB loss with 1000 feet of coaxial cable. Many of my transmitting feed cables are 500-1000 feet long.

If you can find surplus cellular cable, pulled when they change antennas, you can find $1 foot cable that will have less than 1 dB loss on ten meters for 1000 feet.

Or you can build your own open wire line. I built a 1500 foot open wire 450 ohm line that MEASURED about 96%+ efficiency on 4 MHz, including matching transformer losses.  That line was bare solid copper #8 wire. But since that time, surplus 50 ohm heliax is around that actually is better. Even cheap surplus 7/8th inch Heliax will have very acceptable losses at 1000 feet.

73 Tom
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W3KC
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« Reply #8 on: September 30, 2012, 07:04:38 AM »

You might want to look into "Freewave" wireless spread spectrum transponders.  They are often available on the auction site.

http://en.wikipedia.org/wiki/FreeWave_Technologies
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WB6BYU
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« Reply #9 on: September 30, 2012, 08:33:46 AM »

All of your proposed options have been used by hams:

- low loss coax
- open wire transmission line
- RF remote operation, such as Kenwood's "Sky Command" on the TS-2000
- wired remote operation of a station at the top of the hill:  for example,
     a computer control program in the shack that controls the radio.

You might even be able to use a transceiver with a detachable front panel
and a long extension cable, though you would have to keep losses low on
that cable also.

The latter options would require you to run AC or DC power to the site, of
course.

Also note that, while open wire line is often operated at high SWR in common
ham usage, that isn't a good approach for such a long length.  Not only will
losses be higher, but you'll have to retune more often when you change
frequency.  It's best to try to match the line impedance in this case.

Of these options, open wire line would probably be the least expensive, but
running such a feedline is more work than running a length of Romex to provide
AC power.  You'd want a secure weatherproof (and mouse-proof) enclosure
for any radio equipment at the top of the hill.

All of these options require some thought and planning; none are trivial to
do properly, and all can be.  Many modern radios are designed for computer
or other remote control and that gives you a lot more options.


For myself, since I have lots of wire and like trying unusual things, I'd probably
look at a 4-wire 200 ohm transmission line with 4 : 1 baluns on each end, but
that doesn't mean that it is the best solution.
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W8JI
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« Reply #10 on: September 30, 2012, 09:03:10 AM »

People apparently have not looked at the actual loss in coaxial cables and ladder line, and the cost of readily available surplus cable from cellular sites.

I don't know why people think 1000 feet is a long cable. It might be long for RG58 or RG8 cables, but it is not long for 3/4 inch cables or larger. Almost any open wire line, matched or not, would have more loss than typical surplus cell cable pulls or large CATV trunk cable pulls, and that stuff is typically $1 foot or less.

Window line is really not that good for loss. It is more like twinlead and less like open wire, but even very good real open wire lines are not as good as 7/8th inch and larger Heliax cables, and 1000 feet (other than expense) is not unreasonable at all at HF.
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WX7G
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« Reply #11 on: September 30, 2012, 09:32:58 AM »

The original post is "can I operate HF successfully with 1000' of coax feeding my antenna."

The answer is yes. The loss of 1000' of RG-213 at 14 MHz is about 7 dB. Since you are running PSK-31 that's reasonable I think. 100 watts at the radio and 20 watts at the antenna. The 7 dB of line loss increases the receiver noise figure by 7 dB but that will not be a problem on HF.
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AJ4WC
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« Reply #12 on: September 30, 2012, 11:11:55 AM »

I run 20 feet of coax out of to a 1:1 balun from DX Engineering to feed an 80M Skyloop with 330 feet of 300 Ohm twinlead because that's where the best trees were.  I have been very pleased with the performance.  I would definitely consider something like this: http://www.dxengineering.com/search/department/antennas/part-type/baluns-ununs-and-chokes/product-line/dx-engineering-maxi-core-special-line-transformers?autoview=SKU
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WN2C
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« Reply #13 on: September 30, 2012, 11:17:49 AM »

Put up a 'shack' where you want to operate on the property.  Seems to be the easier and cheaper way to go. You could get a Tuff shed for less than what you would pay for the coax !

Good luck with your dilemma
73 de wn2c Rick
« Last Edit: September 30, 2012, 11:26:47 AM by WN2C » Logged
N6AJR
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Posts: 9887




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« Reply #14 on: September 30, 2012, 11:43:19 AM »

I recall an article somewhere, where a gentleman made his own "ladder line" . he put a series of posts from his shack to a distant antenna.  on each post he put a cross  bar  . he put insulators on each T . he ran copperweld from his shack on this home made Twin Lead wire. The posts were set around 100 feet apart or so and the 2 wires were under modest tension. he fed them with coax and a balun on both ends, on to the radio and amp, and one to the antenna.  I think he had about 12 inches spacing on the wires. He was happy with the results, as I remember. I'm just saying...Smiley
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