Fender mount Ham radiation concern
03-19-2017, 11:12 AM
#21
JK Freak
How is your simplex range on the fender mount antenna? We just finished our mobile install and were really unimpressed with our simplex range between home and mobile. Looking for some comparisons.
Here is our base station configuration:
1. Icom ID-51A set to 5 watts (base station)
2. 50' of LMR-400 UltraFlex
3. Diamond X200A mounted in the attic of a one-story house (almost 9' tall, 6/8 dB gain on VHF/UHF). It's an absolute beast; other stations are shocked at our signal with only 5W.
Attachment 668604
We can hit repeaters 30 miles away, full quieting with this configuration, and can barely read repeaters from 50 miles away (with significant static).
Here is our mobile station configuration:
1. Icom ID-5100a transmitting at 50W
2. 11' of LMR-240 UltraFlex
3. Larsen NMO 2/70BK, mounted on the driver-side fender with an Accessories Unlimited AUJ1 mount.
Attachment 668605 Attachment 668606
The test:
My husband drove the Jeep, I stayed at the base station and we did radio checks (VHF simplex) every 30 seconds. We noticed significant drop off at 1 mile, and were barely able to read each other at ~3.5 miles. We've been able to hit repeaters on the mobile ~11 miles away so far (have not tried further yet).
Does this range seem a bit limited to you? Seems we're getting about the same range as a CB. The only issue we can think of is that the bond strap that goes between the engine, firewall, and hood is mostly frayed (we are going to bond the hood at both hinges, soon, and this will be a non-issue).
Thanks!
Here is our base station configuration:
1. Icom ID-51A set to 5 watts (base station)
2. 50' of LMR-400 UltraFlex
3. Diamond X200A mounted in the attic of a one-story house (almost 9' tall, 6/8 dB gain on VHF/UHF). It's an absolute beast; other stations are shocked at our signal with only 5W.
Attachment 668604
We can hit repeaters 30 miles away, full quieting with this configuration, and can barely read repeaters from 50 miles away (with significant static).
Here is our mobile station configuration:
1. Icom ID-5100a transmitting at 50W
2. 11' of LMR-240 UltraFlex
3. Larsen NMO 2/70BK, mounted on the driver-side fender with an Accessories Unlimited AUJ1 mount.
Attachment 668605 Attachment 668606
The test:
My husband drove the Jeep, I stayed at the base station and we did radio checks (VHF simplex) every 30 seconds. We noticed significant drop off at 1 mile, and were barely able to read each other at ~3.5 miles. We've been able to hit repeaters on the mobile ~11 miles away so far (have not tried further yet).
Does this range seem a bit limited to you? Seems we're getting about the same range as a CB. The only issue we can think of is that the bond strap that goes between the engine, firewall, and hood is mostly frayed (we are going to bond the hood at both hinges, soon, and this will be a non-issue).
Thanks!
03-19-2017, 11:46 PM
#22
JK Enthusiast
My husband drove the Jeep, I stayed at the base station and we did radio checks (VHF simplex) every 30 seconds. We noticed significant drop off at 1 mile, and were barely able to read each other at ~3.5 miles. We've been able to hit repeaters on the mobile ~11 miles away so far (have not tried further yet).
This doesn't look right at all. Your simplex range on 2 meters should be much greater, unless you are in a valley, behind a big hill, etc. If you know of someone else with a mobile rig on 2 meters, perhaps you could do a similar test to determine if it's your base setup or mobile setup.
This doesn't look right at all. Your simplex range on 2 meters should be much greater, unless you are in a valley, behind a big hill, etc. If you know of someone else with a mobile rig on 2 meters, perhaps you could do a similar test to determine if it's your base setup or mobile setup.
03-20-2017, 11:05 AM
#24
JK Freak
Agreed, that seems short - testing with a friend, both mobile, both Yaesu 7900's, we reached at least 6-7 miles before it started to drop off, and was still in and out here and there for a little bit beyond that.
I had the Comet 2x4SR antenna mounted on fender; they had a Comet 18" antenna mounted on top of an accessory mast in the rear. This was also in the city as well, with houses/buildings and what not in between.
I had the Comet 2x4SR antenna mounted on fender; they had a Comet 18" antenna mounted on top of an accessory mast in the rear. This was also in the city as well, with houses/buildings and what not in between.
03-21-2017, 08:09 AM
#26
JK Newbie
Join Date: Jul 2012
Location: United States
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
It sounds like there is an issue with your mobile installation. Running 50w mobiles in my Wrangler and our Cherokee, I am able to access repeaters 25-30 miles away in all directions on 2m. Your simplex range should be greater than what you are reporting also, though bad terrain could account for some degradation, as VHF is line-of-sight, and with an indoor base antenna, you are severely limiting that line. If possible, try to get another local ham with a tower mounted antenna to use as a standard of comparison for simplex range. I can actually work 25 miles on simplex to a station with a good outside antenna mounted at 50-60 feet.
04-02-2017, 09:17 PM
#27
JK Freak
It sounds like there is an issue with your mobile installation. Running 50w mobiles in my Wrangler and our Cherokee, I am able to access repeaters 25-30 miles away in all directions on 2m. Your simplex range should be greater than what you are reporting also, though bad terrain could account for some degradation, as VHF is line-of-sight, and with an indoor base antenna, you are severely limiting that line. If possible, try to get another local ham with a tower mounted antenna to use as a standard of comparison for simplex range. I can actually work 25 miles on simplex to a station with a good outside antenna mounted at 50-60 feet.
Will report back.
04-12-2017, 09:20 AM
#28
JK Freak
Due to the mounting location, the antenna is reacting with surrounding metal, and de-tuning it to below the 2m band. See graph of SWR and resonance below.
This might be exacerbated by terrain, too. We're going to keep the antenna at this location and possibly trim it to function better on 2m. Our analyzer doesn't cover UHF, so we're getting a spare whip to install if we ever want to use UHF. Besides, it's a good idea to have a spare element, anyway.
SWR and Reactance (swept from 142.00 - 148.3 Mhz):
FYI the coax checked out OK, and we have .3db loss over ~10 feet as expected for LMR-240 UF on 2m:
-K4GMO
This might be exacerbated by terrain, too. We're going to keep the antenna at this location and possibly trim it to function better on 2m. Our analyzer doesn't cover UHF, so we're getting a spare whip to install if we ever want to use UHF. Besides, it's a good idea to have a spare element, anyway.
SWR and Reactance (swept from 142.00 - 148.3 Mhz):
FYI the coax checked out OK, and we have .3db loss over ~10 feet as expected for LMR-240 UF on 2m:
-K4GMO