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Can't get SWR on 102 whip below 2.0:1
- Thread starter Turbo T
- Start date
here are the Pictures, Sorry about the quality, I only have the phone here with me.
The pictures show the Allen head cap screw that has a plastic insulator cover on it, this goes up inside the base of the antenna mount,and is tightened with an Allen wrench.
The rest is almost the basic set up, but instead of a nut on the outside of the threads of the connector holding everything together, the Allen screw hold`s it.
There is a very tight fitting blind hole drilled in the center of the Allen head screw that the pin of the PL 259 goes up in.
This is the only Quirk I have found with this type of mount....If you install your own 259`s on your coax, make sure that any excess solder is cleaned off of the outside of the pin, and no excess center conductor is sticking above the end of the connector, it must be flush and clean, the hole drilled in the Allen Head screw is very tight.
I would not use any kind of crimp pl259 like the solder-less things that radio shack sells for RG8X ( mini 8) use real full size 259`s with an adapter on the cable end for the smaller cable Dia.
I have yet to break one of these, one tough dohickie
The pictures show the Allen head cap screw that has a plastic insulator cover on it, this goes up inside the base of the antenna mount,and is tightened with an Allen wrench.
The rest is almost the basic set up, but instead of a nut on the outside of the threads of the connector holding everything together, the Allen screw hold`s it.
There is a very tight fitting blind hole drilled in the center of the Allen head screw that the pin of the PL 259 goes up in.
This is the only Quirk I have found with this type of mount....If you install your own 259`s on your coax, make sure that any excess solder is cleaned off of the outside of the pin, and no excess center conductor is sticking above the end of the connector, it must be flush and clean, the hole drilled in the Allen Head screw is very tight.
I would not use any kind of crimp pl259 like the solder-less things that radio shack sells for RG8X ( mini 8) use real full size 259`s with an adapter on the cable end for the smaller cable Dia.
I have yet to break one of these, one tough dohickie
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loosecannon,
I think you could benefit by taking your own advice. But you are right about not many 'cone' shaped vehicles on the roads. But then, there aren't many 'flat' ones either. An irregularly shaped 'ground' works just dandy in most cases.
You may consider that last sentence my "two cents worth".
- 'Doc
I think you could benefit by taking your own advice. But you are right about not many 'cone' shaped vehicles on the roads. But then, there aren't many 'flat' ones either. An irregularly shaped 'ground' works just dandy in most cases.
You may consider that last sentence my "two cents worth".
- 'Doc
After looking at your pics and remembering my S-10 and a similar problem this is what I did and or noticed in your pics. Did you remove the paint from the mounting area on the roll bar to get a good ground for the gumdrop mount? I can't tell by the pics but it looks like you have the gumball mount then a shaft then the spring and on to the 102? If this is correct remove the shaft and mount the spring to the gumball and put the 102 in the spring without using the shaft. Also under the truck where the bolts for the roll bar mount run a ground strap from them to the bed and from bed to frame along with 2 more from the cab to frame on either side of the cab. Rubber bushings where used on the bed to frame mounts on that truck and it is probably a big part of your problem. A quick way to check this is by clamping a set of jumper cables from the frame to the roll bar bolt heads inside the bed of the truck then check the SWR if it helps you know you need ground straps.
I did not deliberately remove any paint but I did ensure bare metal on the inside hole. And the underside doesn't have much paint + also came with a washer that bites into the metal.
I did learn tonight if I place my Wilson 1000 next to the 102 it drops the SWR's by about .5
I did learn tonight if I place my Wilson 1000 next to the 102 it drops the SWR's by about .5
>>>>I did learn tonight if I place my Wilson 1000 next to the 102 it drops the SWR's by about .5<<<<
If this is the case i will say the ground plane is not big enough/or poor contact, i have not put another antenna but my hand close to the radiator to see the the SWR go down.
Seen this at lest twice and both times improved ground lowed the SWR and minimised the affect that my hand had.....some 1 on here cleaver than me can tell you why the SWR will lower when my hand is close
If this is the case i will say the ground plane is not big enough/or poor contact, i have not put another antenna but my hand close to the radiator to see the the SWR go down.
Seen this at lest twice and both times improved ground lowed the SWR and minimised the affect that my hand had.....some 1 on here cleaver than me can tell you why the SWR will lower when my hand is close
the problem is that the antenna only has a DC ground to the truck bed . The antenna is too far above the bed for it to act as an adiquate counterpoise.
You have a great counterpoise close to the antenna ,THE ROOF only one problem .
The antenna only has a DC ground path to it through the roll bar and bed. AS far as rf ground the roof is almost invisible. IF you had a third brake light on the cab you could run a short braided jumper from the bottom of the mount or pl259 to the mounting screw on the light [instant RF counterpoise ] The antenna now sees the roof as you have given a path for an RF ground to the antenna.use a clip lead and try this trick to see if the swr drops when you ground the base of the mount to the cab . I didn't see any light or screws on the cab . you may put a small sheet metal screw near the rubber gasket seal with slicone sealer to ground your braided jumper to the cab .keep it as short as possible. I have done this with good results many times since 1972 mostly on headache racks 4X4 off road vehicles.
YMMV
RCB
You have a great counterpoise close to the antenna ,THE ROOF only one problem .
The antenna only has a DC ground path to it through the roll bar and bed. AS far as rf ground the roof is almost invisible. IF you had a third brake light on the cab you could run a short braided jumper from the bottom of the mount or pl259 to the mounting screw on the light [instant RF counterpoise ] The antenna now sees the roof as you have given a path for an RF ground to the antenna.use a clip lead and try this trick to see if the swr drops when you ground the base of the mount to the cab . I didn't see any light or screws on the cab . you may put a small sheet metal screw near the rubber gasket seal with slicone sealer to ground your braided jumper to the cab .keep it as short as possible. I have done this with good results many times since 1972 mostly on headache racks 4X4 off road vehicles.
YMMV
RCB
Also you have 2 choices provide a Adequate RF ground where the antenna is now mounted OR move the antenna to the bed mounted on an L bracket at the top of the bed rail must be mounted away from the roll bar in the clear.
RCB
RCB
Thanks....of interest something else I tried is I took my 102 down and put the 1000 on the light bar between the gum drop mount and the lamp temporarily, and the SWR's were fine even still. 
Also for giggles and grins I did try wrapping a piece of bare copper wire around the knurled area of the PL259 connector going up to the gum drop and running it to a known ground inside the cab....SWR's didn't change.
Also for giggles and grins I did try wrapping a piece of bare copper wire around the knurled area of the PL259 connector going up to the gum drop and running it to a known ground inside the cab....SWR's didn't change.
Maybe he needs one of these
Fake Hand in Sleeve
Or how about a small 30-75 pf capacitor across the feedpoint?
Ok so if say my antennae has poor ground and the added capacitance of my hand improves the SWR why has my hand have less of a affect on SWR when the ground is good??
Back in the day.... (15 to 30 years ago.......jeeezz i just feel old) i used fit mobile set-ups almost weekly on tractors etc with often glass fibre cab tops and noted this happening.
:laugh:- No one is chatting at the moment.
