[TowerTalk] 80 and 40

Gregg Seidl k9kl at centurytel.net
Thu Jul 10 07:05:24 EDT 2008

Has anyone tried putting a Cushcraft XM-240 and a M2 75/80 meter rotatable 
dipole on the same mast?I'd like to keep the distance from the dipole to the 
beam as close as possible because of windloading on the mast.I also want 
them to work OK though.
    I was thinking about 3.5 to 4 feet because the M2 needs 33 inches for 
its linear loading/support rods.I thought if I'd go a bit above that.
    Also if I did that I could reach the support ropes for the 40 meter beam 
while standing on the top plate..or if I really had to I could put my mast 
steps on the mast and climb that a little bit.I REALLY don't like doing that 
    My mast is 1026 DOM 2 inch by quarter inch wall.
On a different note about lengths of towers.I'm having the crane come back 
and do some more tower work and I getting ready to top off my 75-80/160 
tower.I'm using the Array Solutions box.It requires the insulated tower to 
resonate at 3.8 or so and then uses loading to get it to go to 3.5 and 
1.8.I'm trying to get it as close as possible length wise.The tower is made 
from 5 straight sections and 1 tapered Rohn 25.I know that is not long 
enough and plan to use a peice of conduit inserted in the tapered section to 
bring it into resonance.My question is about how long should I install the 
pipe?Could someone please model that for me?
    One more thing,I ( crane ) installed my new 85 foot Rohn 45 2 weeks 
ago.I've been working on getting the conduits buried AND on getting it 
grounded as best I can with little cost while doing a reasonable job.I 
truely believe if you get a DIRECT hit nothing will help that but I think 
nearby's can be handled.I ended up with 4 ground rods driven all the way 
down into trenches I had dug for the grounding.I used some #2 copper wire I 
had aquired from a freind.I just used burial rated clamps and spaced the 
ground rods out 10 feet and connected them on 2 of the tower legs.Measured 
the resistance and it is VERY VERY low so I have good connections.Last 
Monday night we had a pretty good little thunderstorm roll thru here and I 
was in my shed building my 75/80 meter dipole and talking with my wife who 
was "helping" me.We decided to stop and just watch the storm roll thru when 
suddenly I saw my new tower take a direct hit and then saw a return stroke 
go from the tower back into the sky.Cool very cool but I thought about the 
dipole I had installed for FD with the cable going into the shack,it wasn't 
connected to anything though.I ran in the house and went in my shack and 
expected to see flaming hulks of radios and amps.NOTHING HAPPENED.I was so 
happy I gave my wife a big kiss!!I waited till the next day and sunshine to 
go check out the tower and I couldn't see ONE sign of anything happening to 
the tower or grounds,its like it didn't happen.I must have done something 
right.My point is to do what you feel comfortable spending on your grounding 
of towers and then maybe spend a little time praying. Thanks for reading and 
hopefully someone can help me out with my questions.  Gregg K9KL 

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