[SixClub] Recommended Coax?

[Roger (K8RI)]

Hi Doc,

On 6/16/2010 12:22 PM, kd4e wrote:
> I am slowly getting my Ham setup in place in the
> new QTH ...
>
>    
I've been doing that for over 25 years at this QTH.
> There is a 25' run from the operating desk to
> the Polyphaser lightning protection device
> mounted on the exterior metal shell, so that
> section of coax is not exposed to the weather,
> if that is relevant.
>
>    
Only whether it needs sealing or not.
> What is a reasonable cost preferred coax you'd
> recommend that I use for this short run 6m,
> and also for 2/440?
>    
For the short, interior run I'd use Davis BuryFlex(TM)  and I also use 
it for rotator loops.
It's loss figures are very close to 1/2" hard line/Heliax and LMR-400.
I do not like 1/2" Heliax as I find it to susceptible to kinking.
I do like the larger versions of Heliax, but they are both large and 
heavy so I don't have any in use.

OTOH I do not like the ultraflex versions of LMR cables as the jacket is 
rubber like and not UV tolerant. It's also a bear to strip.
For a total of 100-125' run I have used LMR-400 all the way up through 
440.  I've since changed to LMR-600 (except for rotator loops and from 
the patch panel to the rigs)  as I got it at a good price.
I use Davis BuryFlex(TM), LMR-600, and several forms of RG-8X in the system.

I have never run into the problem with galvanic action on the shields 
"except" where the N-Type connectors leaked and the only place this 
happened was with the ultra flex versions. The water got in via the C3i 
power dividers for both 144 and 440. Taking them apart showed they had 
water up to 2" deep in them at one time or another. If they hadn't 
sealed the bottom all would probably have been fine.  I've since gone to 
nearly all crimp connectors rather than clamp. I've also come up with 
some different end sealant for the power dividers.  BTW I never had the 
KLM power dividers leak and they are probably about 30 years old.

What I did have here (I'm in the midst of repairing antennas and 
changing antennas) is: runs of LMR-600 from both the house and shop to 
the 6-pack at the base of the tower for HF. Actually I have two runs for 
HF from the shop and house as the spare rig gets moved around a lot. 
Following the 6-pack I have some short runs to the remote antenna 
switches for 40 and 75 near the bottom of the tower. From these I use 
either Davis BuryFlex to the 75 meter slopers, and RG-8X to the 40 meter 
slopers. I'm not worried about loss at 7 MHz and the 8X will handle the 
legal limit with low SWR which is why I use BuryFlex(TM) for 75. I use 
three runs of LMR -600 up the tower for 160, the tri-bander, and six 
meters.
For 144 and 440 I have 3 runs of MR 600 from the rigs to the antennas 
except for the Davis BuryFlex rotator loops. Of these two go to the 144 
and 440 arrays and one goes to the Diamond 144/440 side mounted 
vertical. There are separate runs for 144 and 440 as I often have both 
running at the same time. The house and shop each have their own side 
mounted diamond vertical and will be using another switch for the 144 
and 440 arrays.

The tribander is getting moved to a 50' 25G at the West end of the shop 
and "I think" replaced by a used Force 12 C-19 XR which is coming off 
the tower of a local ham today who is moving to a new home.

All coax runs going up the tower have their shields grounded at the top 
and bottom of the tower. I do this using bulkhead connectors. The loss 
from the additional  "good" connectors is almost immeasurable and the 
lightning protection is priceless.

Loss in LMR 400 at 440 is just under 2.7 db per 100'
Loss                     at 144 is about 1.4db per 100'
So for longer runs 7/8" Heliax is considerably better. Even the 1/2" 
Heliax is 1 db better at 440, plus if you are so inclined the 1/2 heliax 
will handle the legal power limit while LMR-400 is only rated for 830 
watts continuous at 450 MHz.
LMR 600 like 1/2" Heliax has a loss of about 1.7 db in the 440 band and 
it's available new some where in the range of $1.30 to $1.60 per foot.
I paid $1.29 a bit over a year ago.

You can often find the 1/2 and 7/8" Heliax as pulls from commercial 
installations at very good prices and some times for free, but you may 
have to hunt for a while to find it.

73

Roger (K8RI)
> Or is that run so short that it doesn't really
> matter?
>
> Once outside then the run is about 100' to the
> planned 2/440 location and the same to the 6m,
> (maybe 125-150' depending on the routing). What
> coax is recommended for that?
>
> Note:  The outside runs will run along the top
> of a PVC fence then along the top of a steel
> shipping container - then up the masts which
> are strapped to the steel container - those
> antennas will eventually get rotators.
>
>
>