Well I opened up a can of "get with it" and got-er-done today. My truck is a 2009 Ford Ranger Sport. My radio is an old 70's President Grant. My coax is an 18 ft Wilson super mini 8. The antenna mount is a 3/16' stainless steel '"L" bracket with a Wilson extra heavy duty assembly stud. The antenna is mounted to the passenger side of the bed at the rear by the tailgate. I ran the power wires for the radio directly to the battery and ran the coax down the stake pocket to the frame into the underside of the cab through a rubber plug, under the rubber floormat into the back of the radio. The radio for now is using a sawtooth hump mount so I can remove the radio at night. I'm waiting on my 5' STT5, it should be here this week, and my QD2 quick disconnect.
Just for grins and giggles I rounded up three fiberglass antennas I found at work stashed away in a corner and tried them out.
All three are 3' top loaded and probably 20 years old. Two are generic with no brand name but one is definately a firestick. I went to an open field and hooked up my Radio Shack meter with a 12 ft run of RG/58 (I know 12' is a little long but it's all I had and I haven't found anybody that sells a 2 ft jumper cable around here). The Firestick was past 3 on both channel 1 and 40. One of the generics was at 3+ on channel 40 and 2.5 on channel 1, and the other generic was at 1.2 on channel 1 and 3+ on channel 40. If I understand SWR metering correctly the results tell me that those antennas are too long for the setup since the readings (except for the firestick) were lower on channel 1 than on channel 40. When I checked the power output of the radio it measured a hair less than 5 watts. Another issue to deal with is the engine noise. It's not a whine but sounds more like plugwires broadcasting. If you're old enough to remember the days when cars only had AM radios you know that sound. The noise increases with the engine RPMs but is completely absent and quiet with the engine turned off. Is this noise the injectors, the plugs, or plugwires? I know I need to do some grounding work and will. The noise settles down considerably when I turn on the noise blanker button on the radio. I checked the antenna mount to ground with an ohm meter and I've got good ground there but I also have about 60 ohms from the antenna stud to the frame as well. Is this normal? ? Since the SWR's were so high on channel 19 I didn't try to talk to anybody although I was hearing plenty of radio traffic from the truckers on I-40.
My concerns are If a 3' antenna is too long, what's gonna happen when I put the 5 footer with the quick disconnect on there? Do I need to ground the bed to the cab? Looking for some experienced input here.
my new install
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cfox
- 6 PILL USER
- Posts: 66
- Joined: Feb 12 2011, 14:53
- Real Name: curt
- Radio: President Grant
- Contact:
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Radio 75
Chillax there Fox!
Wait until your new antenna gets there and repeat the test.
Now, a word about jumpers and SWR meters. Some folks think you can "tune" your antenna system by using different lengths
of coax. This is not true!!! Your SWR will not change at all no matter what the length of coax, within reason. I mean, you
have to take coaxial cable loss into the equation too. Using a 20' jumper is no problem.
Now, with that being said, using a 20' jumper can be a problem.
Are you coiling the coax up? That can and will effect the way the SWR meter displays your results, as well as using 1/4 wavelengths or
multiples thereof, (electrical 1/4 wavelengths, not physical 1/4 wavelengths) because of the current nodes along the antenna system.
Just because your SWR meter reads differently with different lengths of coax does not mean that your antenna system is more,
or less, efficient.
Bottom line is, make your coax run to your antenna, and before you mount the antenna, plug a dummy load into where the antenna
will be and check the SWR. Is it less than 1:1??? Then you are good to go. Mount the antenna. If the SWR is higher on the upper channels
and lower on the lower channels, it is too long.
If the SWR is lower on the upper channesl and higher on the lower channels, it is too short, and you must somehow ADD length to it.
Trimming an antenna for the best SWR is a compromise.
Trimming an antenna for resonance is a mystery, just ask 'Doc.
It's not rocket science for the most part, and anything under 2:1 is OK. Under 1.5:1 is good to go!
Wait until your new antenna gets there and repeat the test.
Now, a word about jumpers and SWR meters. Some folks think you can "tune" your antenna system by using different lengths
of coax. This is not true!!! Your SWR will not change at all no matter what the length of coax, within reason. I mean, you
have to take coaxial cable loss into the equation too. Using a 20' jumper is no problem.
Now, with that being said, using a 20' jumper can be a problem.
Are you coiling the coax up? That can and will effect the way the SWR meter displays your results, as well as using 1/4 wavelengths or
multiples thereof, (electrical 1/4 wavelengths, not physical 1/4 wavelengths) because of the current nodes along the antenna system.
Just because your SWR meter reads differently with different lengths of coax does not mean that your antenna system is more,
or less, efficient.
Bottom line is, make your coax run to your antenna, and before you mount the antenna, plug a dummy load into where the antenna
will be and check the SWR. Is it less than 1:1??? Then you are good to go. Mount the antenna. If the SWR is higher on the upper channels
and lower on the lower channels, it is too long.
If the SWR is lower on the upper channesl and higher on the lower channels, it is too short, and you must somehow ADD length to it.
Trimming an antenna for the best SWR is a compromise.
Trimming an antenna for resonance is a mystery, just ask 'Doc.
It's not rocket science for the most part, and anything under 2:1 is OK. Under 1.5:1 is good to go!
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cfox
- 6 PILL USER
- Posts: 66
- Joined: Feb 12 2011, 14:53
- Real Name: curt
- Radio: President Grant
- Contact:
Where do I get a dummy load? Can I buy one somewhere or make one?
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Radio 75
Yes!
I don't think the Shack sells them anymore, but I have seen them on Ebay, and I'm sure some of the CBRT sponsors
carry them. Making one is easy too. All you need are some 50 ohm 5 watt carbon film resistors. Do NOT use wire wound
ceramic type resistors. Just use 3 of them together. Twist the legs together, insulate them with shrink tubing or tape and solder them to the center pin of a PL-259. Bend over the other end of the three legs and solder them to the barrel of the PL-259.
Make sure you don't touch the resistors when you transmit!
Also, do a google search on salt water dummy loads. They look easy to make, and downright cheap too!
I don't think the Shack sells them anymore, but I have seen them on Ebay, and I'm sure some of the CBRT sponsors
carry them. Making one is easy too. All you need are some 50 ohm 5 watt carbon film resistors. Do NOT use wire wound
ceramic type resistors. Just use 3 of them together. Twist the legs together, insulate them with shrink tubing or tape and solder them to the center pin of a PL-259. Bend over the other end of the three legs and solder them to the barrel of the PL-259.
Make sure you don't touch the resistors when you transmit!
Also, do a google search on salt water dummy loads. They look easy to make, and downright cheap too!
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cfox
- 6 PILL USER
- Posts: 66
- Joined: Feb 12 2011, 14:53
- Real Name: curt
- Radio: President Grant
- Contact:
sounds simple enough, thanks.
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cfox
- 6 PILL USER
- Posts: 66
- Joined: Feb 12 2011, 14:53
- Real Name: curt
- Radio: President Grant
- Contact:
WOW! what a difference a good antenna makes. I installed the STT5 today and I'm delighted and somewhat suspicious that the SWR's were so low. They are pretty much flat across the band , less than 1.1...Is this possible? RX is way better, the noise level went down and the engine noise is practicaly non existant. I'm impressed. Thanks for all your help guys.
