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bad swr reading

dway87

Member
Oct 14, 2006
88
2
16
San Angelo,Tx / Fredericksburg,Tx
i just installed a dual phased antenna system with 4' wilson fgt fiberglass antennas with 5" hd springs. i have them mounted on each side of my toolbox. the readings that i get are well over 3 throughout the board! any suggestions?
 

as FL native is implying, the springs are making the antenna too long. if you had a radio that went WAY down, like a 4800/6900/158/2950dx/etc, you'd probably find you're nearer 1.1:1 at 26.000, or even lower.
 
dway87 said:
any suggestions?
Yes, use a SINGLE antenna! Your dual antenna set-up is most likely too close to each other to give you the desired results.

I recommend the P-10K mounted in the center of your tool box (if you refuse to mount it on the roof).

I don't even recommend dual antennas for over the road trucks! SINGLE ANTENNA - SINGLE ANTENNA!!!
 
Master Chief said:
dway87 said:
any suggestions?
Yes, use a SINGLE antenna! Your dual antenna set-up is most likely too close to each other to give you the desired results.

I recommend the P-10K mounted in the center of your tool box (if you refuse to mount it on the roof).

I don't even recommend dual antennas for over the road trucks! SINGLE ANTENNA - SINGLE ANTENNA!!!

sounds good. maybe that's why i had a lot better results in the past with a single antenna. thanks for the advise.
 
Co-phased antennas need to be at least 9-10' apart from each other to get acceptable SWR's. Oterwise, the antennas are just going to interfere with each other. Mirror mounting the antennas will give a stronger signal side to side, instead of front to rear like you want. I've found that a good single antenna actually works alot better than duals as far as performance goes. Looks are a different story though, & dual whips on the mirrors looks great, but...
 
if you really want the dual look just connect 1 antenna . do not use the coax you have now with one antenna . always use the best coax you can .

id check the swr before i went into grounding stuff . if it tunes nice and low and your tx/rx is good i wouldnt worry about it .
 
dway87,
Should you ground things? Yes, and maybe no. If the antenna is designed to work without a ground then it isn't necessary. If it's like most mobile antennas, start thinking about grounding things.
Lots of "if"s, "and"s, and "but"s in that! It deals with most vertical mobile antennas being only 'half' of the antenna 'system', the vehicle being the other 'half'. If the antenna 'sees' enough of that 'other half' without doing a lot of grounding, then fine. If not, well, start grounding. How do you tell? The easiest way is try it and see. If it works, don't fix it. If it doesn't work... start 'fixing' it.
- 'Doc
 
BOOTY MONSTER said:
if you really want the dual look just connect 1 antenna . do not use the coax you have now with one antenna . always use the best coax you can .

id check the swr before i went into grounding stuff . if it tunes nice and low and your tx/rx is good i wouldnt worry about it .

i was thinking about this idea but wasn't sure if the other antenna would still interfere with the one that is connected. i am just gonna go and see all the different factors that will work.
 
dual antenna whips don't even get out far :)
and yes 9' or more apart(12' Co-phased bought out of a place in
Louisiana :p)...I use mine grounded as a receive,but both work as transmit to but not more then 400 watts..
(but are both tuned for 27.16).Tuning screws on the top and a dummy load (1 antenna at a time). I like the lights at night :p

BOB Wrote;
dway87,
Should you ground things? Yes, and maybe no. If the antenna is designed to work without a ground then it isn't necessary. If it's like most mobile antennas, start thinking about grounding things.
Lots of "if"s, "and"s, and "but"s in that! It deals with most vertical mobile antennas being only 'half' of the antenna 'system', the vehicle being the other 'half'. If the antenna 'sees' enough of that 'other half' without doing a lot of grounding, then fine. If not, well, start grounding. How do you tell? The easiest way is try it and see. If it works, don't fix it. If it doesn't work... start 'fixing' it.
- 'Doc


For example; a trucker 5000 ..I tried this sucker on my van with a
5" and a 10" shaft and the correct stinger size, and on my MFJ-259 meter couldn't get it lower then 1.5 SWR and 45 ohms....to much ground I said maybe? (mag or stud mount)... now on a mirror mount with a 10" shaft it works great works great as you know the coil pack needs to be above the truck or van! .Even the 2 Monkey made mm9's I have work ok on a mag or stud mount (1.6 SWR and 45 ohm) and that was with moving the coils up towards the top of the antenna a tad. Now I ask myself on these to much ground or not enough?(well I will see over the weekend when I attach 3- 4' wires to the base under the lining of the roof to act as my radial ground). ( I got this idea from running the tram tri-mag in the house with 3- 4' ground radials on the bottom of the mag mount bolts)right now I am running a Black Al Ca'pone on a tram tri- mag and it shows 1.1 and 50 ohms SWR...Now when I put it on the mount in the center of the van (PL259 to stud mount setup BTW)and try to re-tune my SWR is 1.5 at 45 ohms and can't be lowered...

peace out for now :)
 
i tried fdual wilson silverloads with 75 ohm coax mounted on the the old style metal mirriors.swrs were ok.between 1.3-1.6
on just cb band.switched to a single antenna with 50ohm coax
mounted on passenger side swrs went down to 1.2-1.4
and rx /tx was better.id mount it on the mirriors [if possible]
if not then definately id go on the tool box.the roof would probaly yeild the best results.
 

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