kewlkeed
join:2005-02-05
Knowlton, QC
| Max coax length for HF?
Hello all!
Was just wondering if there are any guidelines for the maximum length of the coax going to an HF antenna. I am in the process of getting a new house, but I'd like to space the antenna away from the house by about 200 feet. Is something like this possible without a ton of loss? Or should I consider something else?
The only rig I'll be running is a FT-101ZD for the moment, so no massive amps or anything. |
|
Splitpair
Premium
join:2000-07-29
Cow Towne
 ·T-Mobile US
·T-Mobile US
 ·AT&T Southeast
| said by kewlkeed  : but I'd like to space the antenna away from the house by about 200 feet. Is something like this possible without a ton of loss? Or should I consider something else? With RG-8 you would have under 2dB of loss which is quite workable.
»www.ocarc.ca/coax.htm
Wayne
--
Yeah, there's a storm on the loose, sirens in my head
Wrapped up in silence, all circuits are dead
Cannot decode - my whole life spins into a frenzy
|
|
kewlkeed
join:2005-02-05
Knowlton, QC
| reply to kewlkeed
Thanks!
The stuff I've got is RG-8/U which isn't listed on there. But it looks like I won't be having a serious problem with it. Hopefully the run is more like 100 feet but I want 200 to give myself some leg room.
Should be interesting! |
|
Tzale
Ron Paul 2008 - Proud Conservative
Premium
join:2004-01-06
NJ, USA
 ·Verizon FIOS
 ·Optimum Online
| said by kewlkeed :Thanks! The stuff I've got is RG-8/U which isn't listed on there. But it looks like I won't be having a serious problem with it. Hopefully the run is more like 100 feet but I want 200 to give myself some leg room. Should be interesting! RG-8 is great for HF, but be careful with it at those lengths on VHF.. Some serious loss the higher in frequency you go...
--
Neoconservatives (G.W.B) are not real conservatives. A conservative believes in defending the Constitution. First they ignore you, then they laugh at you, then they fight you, then you win. - RON PAUL 2008 »www.usconstitution.net/const.html
|
|
kewlkeed
join:2005-02-05
Knowlton, QC | reply to kewlkeed
Yeppers.
Hehehe I do a lot of stuff at 2.4Ghz. For fun I had to calculate the loss at 200 feet using RG-8. Hehehe I'd have better chance loading it into a tree trunk. |
|
Ender3rd
join:2001-07-15
East Granby, CT
·Cox HSI
| reply to kewlkeed
As others have already stated, you won't notice any major loss issues at HF. Most guys would love to get their antennas 200 feet from the house to avoid RFI issues and pickup of noise from the usual home appliances! Good luck with the installation!
Rob W1AEX
--
My Jeep is not an SUV. Your SUV is not a Jeep. |
|
Splitpair
Premium
join:2000-07-29
Cow Towne | reply to kewlkeed
Another possibility is if you are really concerned about loss would be to place a wideband pre-amp at the antenna and using two antenna relays by-pass it on transmit.
Wayne |
|
GeekGirl1
The Medium IS the Message
Premium
join:2007-01-28
Morrisville, PA
·Verizon FIOS
·Verizon Online DSL
edit:
March 24th, @09:34PM
| I'd worry about intermod / inteference from a wideband pre-amp without any way to take it out of line when not needed. More complicated setup - you need a power supply and a way to tell the difference between a dead preamp and no signal due to no band activity.
At HF, the atmospheric noise is so high, you don't really care about loss as much as problems due to front-end overload. IOW, 3rd order intercept instead of noise figure. At UHF and higher, it's the other way around.
I'd take the loss of a long coax run. Just use a higher gain antenna... |
|
kewlkeed
join:2005-02-05
Knowlton, QC
| reply to kewlkeed
Thanks guys(And GeekGirls of course)! Keep the suggestions coming! I like the thread. I can't wait to see/hear what the finished product is once I get the new house. I'll be sure to post some pictures.
Here's a nice continuation, has anyone found a certain type of antenna to perform better at a long run than others? I know this will probably come down to a preference thing, but hey who knows. |
|
n1zuk
Circular Reasoning Works Because
Premium
join:2001-10-24
South Burlington, VT
 ·Future Nine Corpor..
·Comcast
·ViaTalk
·Packet8
| reply to kewlkeed
At HF frequencies (even 10M), 200' really isn't that long a run where coax loss is that significant. As your total loss is the sum of a number of things (switching, connectors, matching) using a quality coax with well assembled, quality connectors will mitigate most of the loss you will see in a 200' run.
Many "Big Gun" contest stations I've seen with multiple towers (or just one situated far from the 'shack') will use hardline for most of the run between building and tower. They use coax at each end. But one of the main reasons they choose this path is that they can bury the hardline without much difficulty.
There was a time when a person could get hardline just for the asking. Cable companies would literally give the short runs left on the spool, as it is APITA to splice. Those days I believe are gone, as the price of scrap metal has skyrocketed... 
--
New to Forum Life? Click here and learn. |
|
Splitpair
Premium
join:2000-07-29
Cow Towne
·T-Mobile US
·T-Mobile US
·AT&T Southeast
edit:
March 25th, @02:00PM
| said by n1zuk : Cable companies would literally give the short runs left on the spool, as it is APITA to splice. Is it really worth using CATV hardline with what is involved in matching it's 75 ohm impedance to what normally is a 50 ohm system?
Wayne
--
Yeah, there's a storm on the loose, sirens in my head
Wrapped up in silence, all circuits are dead
Cannot decode - my whole life spins into a frenzy
|
|
drjim
Premium,MVM
join:2000-06-13
Torrance, CA
clubs:
| The impedance mismatch using CATV hard line is vastly overstated. At worst you get 1.5:1, which is perfectly acceptable. I've used it for long runs on my satellite station, and it's great stuff. VERY low-loss, but kind of a pain to put connectors on.
--
One man's Magic is another man's Engineering. |
|
KA3SGM
- -... ...- -
Premium
join:2006-01-17
West Chester, PA
clubs:
·Verizon FIOS
| reply to kewlkeed
Same size as RG-8 but better performance would be Times Microwave Systems LMR-400 coax.
It uses the same connectors as generic RG-8, and doesn't collect water like Belden 9913 and it's clone variants.
It's a lot lighter and cheaper too, as the center conductor is copper plated aluminum, instead of 100% copper.
For HF it is still probably overkill unless you are up on 10 Meters and are running 300+ feet of it.
You can direct bury it, but the LMR-400-DB version is flooded to keep water out in the event that the jacket gets cut.
Although for anything run underground, it's best to bury conduit and pull the cable through it.
Just make sure that if you go to bury anything to call your local Utility 'One-Call' number and have them locate and mark any existing buried utilities.
LMR-400 is great for runs of 100 feet up to 70cm, but I tend to break away towards the LMR-600 type for longer runs at 70cm,
and for anything at 23cm and above, because it is less than $1.50/ft and the connectors are around $10 each..
Anything better than that is probably Andrew 7/8ths Heliax @ $7.00/ft and $50 each for the connectors.
--
"Lithium is no longer available on credit" |
|
Axilla
Finger, Finger
Premium,Mod
join:2001-03-26
Schofield, WI
clubs:
Host:
Mediacom
Weather
| reply to drjim
said by drjim :The impedance mismatch using CATV hard line is vastly overstated. At worst you get 1.5:1, which is perfectly acceptable. I've used it for long runs on my satellite station, and it's great stuff. VERY low-loss, but kind of a pain to put connectors on. Thats a good point, on HF you never have a perfect match, especially running different bands only one will be truly resonant.
But what do I know; I live in an apartment and use a longwire.  |
|
w4jle
Broadband Ain't A Womens Musical Group.
Premium
join:2002-03-23
Gilbert, SC
·PBT Telecommunicat..
| reply to kewlkeed
Why use coax? It is great to get thru the wall of the house, then go to ladder line. Less loss than any of the high dollar coax. Wind a couple of baluns and your good to go!
--
Fred W4JLE - Professional curmudgeon - Lexington SC |
|
burner50
Pinlifter
Premium,VIP
join:2002-06-05
On the lead
·Mediacom
·FrontierNet Intern..
| reply to n1zuk
said by n1zuk :There was a time when a person could get hardline just for the asking. Cable companies would literally give the short runs left on the spool, as it is APITA to splice. Those days I believe are gone, as the price of scrap metal has skyrocketed... And cable is STILL worthless... Splicing hardline is easy if you have the hundreds of dollars of coring tools and make sure the center conductor is clean.
hmmm... this conversation makes me wanna dig out my CCOR pocket guide... |
|
burner50
Pinlifter
Premium,VIP
join:2002-06-05
On the lead
·Mediacom
·FrontierNet Intern..
| reply to KA3SGM
said by KA3SGM :Just make sure that if you go to bury anything to call your local Utility 'One-Call' number and have them locate and mark any existing buried utilities. Great advice, and also remember that they probably wont locate any of your private lines like landscape lighting, electric/cable/phone to the garage, built in grill, etc... |
|
KA3SGM
- -... ...- -
Premium
join:2006-01-17
West Chester, PA
clubs:
·Verizon FIOS
| said by burner50 :said by KA3SGM :Just make sure that if you go to bury anything to call your local Utility 'One-Call' number and have them locate and mark any existing buried utilities. Great advice, and also remember that they probably wont locate any of your private lines like landscape lighting, electric/cable/phone to the garage, built in grill, etc... Yup, your own buried lines are your responsibility, the One-Call system only locates Public Utilities and Semi-Public pipeline companies.
Keys Capt might want to include this in the Glossary or FAQ, that there is a national movement to dedicate the phone number 811 to Statewide 'One-Call' organizations.
Even if you are simply digging to plant a Garden, or planting a Tree, the law dictates that you must call the local One-Call system and request that they locate and mark the underground utilities.
The call only charges the utilities and professional contractors for their location efforts, it is a free call and a free service to the individual homeowner.
You have to give them 3 working days to locate any buried utilities before you grab a shovel and start digging.
Be responsible, possibly save your own life, and call 811 before you dig. 
--
"Lithium is no longer available on credit" |
|
burner50
Pinlifter
Premium,VIP
join:2002-06-05
On the lead | AND I have dealt with some small towns with "municipal" water services, except there is no city employees to locate the water lines...
Time for a divining rod then (ACTUALLY WORKS)
BUT THATS ANOTHER STORY... |
|
KA3SGM
- -... ...- -
Premium
join:2006-01-17
West Chester, PA
clubs:
·Verizon FIOS
| said by burner50 :AND I have dealt with some small towns with "municipal" water services, except there is no city employees to locate the water lines... Time for a divining rod then (ACTUALLY WORKS) BUT THATS ANOTHER STORY... Had that back here a little more than 1 month ago.
My neighbor across from me had their plastic water line fail under the street, and I had probably 10 of the local water company's Plumbers walking around the neighborhood with 2 copper 90 degree bend Divining Rods looking for the main, the shutoff, and where to dig to find the bad line.
And they were dead on as to where to dig, those Divining rods are amazing tools.
--
"Lithium is no longer available on credit" |
|
