Today I made more progress.. Connected the phasing lines (LMR-400 @ 317"
each) from the antenna feed points to the M2 1/2 wave divider and fastened
them all to the H-Frame. Weather sealed every connection with an Andrew
weather seal kit. From the Divider feed I have a 20 foot run of LMR-400 for
the rotor tail line that after being secured runs down the tower to about 4
feet above the ground. The Jack Screw has been mounted and tested at the
base. The way I have the elevation fixture setup the lowest I can get is
right at 3 degrees, can't get down to Zero. I feel this is fine as I can't
see the horizon anyway due to lines of tall trees at a distance (1/4 mile)
and 3 degrees will be just as the moon clears the tree line. I can get a
full 90 degrees to the other extreme. Rolled out the LDF7-50 (1 5/8") from
the base of the tower with 8 feet excess all the way to the shack entrance
(35 feet excess at that end) Boy dragging 170 feet of LDF7 is a job in
itself!!!!. Also laid out a run of LDF4-50 (1/2") the same distance, Along
with 2 runs of 8 conductor rotor cable. A contractor will be coming by early
next week with a "Ditch Witch" to create a nice 132 foot by 3 foot ditch for
the cable runs to the tower from the shack entrance. I plan to lay two 4"
PVC pipes for the feed lines and other control lines. And that's were I sit.
I plan to mount a weather proof box at the tower base around 4 feet above
ground. I'll run lines from all the antenna feeds to this box through Type-N
feed through bulkhead connectors in the top, and the feeds lines from the
shack will be feed to Type-N feed through bulk-head connectors in the
bottom. Same with the control wires, but using terminal strips inside the
box. This will allow me to mounts relays, preamps, and other devices in the
box and tap them into the lines as needed, or bypass devices if need. If
needed I can run a small jumper from the top bulk-head to the bottom
bulk-head and take a pre-amp out of line as such. Also makes grounding the
feeds lines and tower to a single point easy. I have three 10 foot ground
rods, one on each leg of the tower, that will be utilized here all attached
to an Andrew copper grounding bar mounted on the tower. I plan to add a
couple of extra bulk-head feed through just in case for some reason I need
to add something later.
I plan to do the same at the shack entrance as I have a 60 foot tower with 5
Tropo antennas. This will allow me to bring ALL the feed lines to one
central point for grounding and in case of a bad storm, I can disconnect all
feeds outside the shack within minutes, or even add lines for later..
Now for the questions...
I have two 8 conductor rotor cables laid out so far. One will feed the AZ
rotor, three wires from the 2nd cable will handle the EL indicator and 2
wires for the jack screw. This leave 3 open wires. I assume to play it safe
I should run another run of 8 conductor wire to give me 10 open wires for
control down the road for relays, pre-amp feed power feeds etc etc.. Or
could I need more in you view?
How much loss am I gaining on the TX and RX line using these bulk-head feed
through and am I causing more loss then needed for what I'm doing.
When setting the Array/Rotor to "North", is this magnetic north or a MAP
north? Its several degrees difference here *hi*.
Anyone offer any suggestions on stream lining or improving the feed line
system I have laid out for better NF and or gain on either TX side or RX
side.
System details will be as follows.
Forgive errors as I don't have a PHD in math and I'm learning, and using
printed figures
Cable loss figures done here. http://www.ocarc.ca/coax.htm
KLM 4X18s ---> Phasing Lines 317" each or 26.41 feet X 4 = 105.64 feet
Phasing line loss @ 1.571 db
Phasing lines ---> M2 1/2 wave Power Divider.
Power Divider loss (?)
Power Divider ---> 20 feet LMR-400 (Rotor Tail)
LMR-400 Loss @ 0.297 db
(Assuming direct feed through Box here)
Rotor Tail ---> Bulk-head --> Small 10" 1/2" line to bottom bulk-head. Loss
(?)
Bottom Bulk-head --> 132 feet LDF7-50
LDF7-50 loss @ 0.335 db
LDF7-50 ---> Bulkhead ---> 10" X 1/2" Run -->bulk-head
Loss (?)
Bulk-head --> 20 feet LDF4-50 --> Radio
Loss 0.1 db
Loss calculated 2.303 db loss in the TX line, radio to Antenna with just
know variables.
Planned LNA to use and put in the Tower box is a SSB SP-2000 MODEL FREQ. NF
MAX GAIN-Adj. Filters
SP-2000 144.0MHz. 0.8 10-20dB HELICAL
No insertion loss listed.
Lets not forget the LDF4-50 (10 feet?) used between the AMP and the Radio
when it's back inline. The RX line will mimic the TX line, except it will be
LDF4-50A instead of LDF7-50. But I assume the LNA at the array end will make
up that loss just fine.
So before I start cutting final lengths of the feed lines, and punching
holes in Boxes for bulk-heads.. Comments ?
Dave
Starting to look like more then a pile of parts here now.
N5ITO / EM23
http://david.davidv.net
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