NMO questions

[KY4CQ]

I was running a Tram 1180 on a NMO fender mount on my 2020 Silverado temporarily until I got my new antenna (Larsen NMO 2/70SH) in. Out of curiosity, I put the 2/70sh on my fender mount and it seems to perform pretty rough compared to my 1180. To be fair, it's a compromised antenna vs the 1180 which is a 1/2 wave on VHF and a 5/8 over 5/8 on UHF. My 1180 however keeps hitting the parking deck at work, so I needed something smaller. The end goal has always been to drill a hole and mount an antenna, but if I won't see much improvement of my 2/70sh on the roof vs on the fender, I'll keep the fender mount. How much of a performance increase can I reasonably expect on the NMO roof mount?

 

[n5ims]

According to this Larsen chart, you'll get about 3dB of loss using a fender mount vs a mount on the center of the roof mount. Check the picture for the comparisons.

Mobile Antenna Placement | KV5R.COM

 

[mmckenna]

The "center of the roof" mount also gives you a better radiation pattern over the fender mount.

 

[Station51]

Yup, what McKenna said. Center roof will give you a little more height, but also 360 degrees. Your fender mount is directional toward the back of your truck. If you're doing it yourself, you should be able to feed the coax toward the right corner by the rear window and then run in along the door up to where the radio is. The plastic door sills just pop off. Some people pull the rear brake light to direct the coax but I only did that the first time lol. OR, have it done by a radio shop

 

[mrweather]

FWIW, I have the NMO2/70SH and was never really that impressed with the performance. A regular 1/4 wave whip worked just as well (on both bands) and was much cheaper.

Now, its big brother the NMO2/70 is light years ahead and is the better comparison to the OP's Tram antenna.

 

[prcguy]

Yup, the big open coil NMO 2/70 is a great performer.

FWIW, I have the NMO2/70SH and was never really that impressed with the performance. A regular 1/4 wave whip worked just as well (on both bands) and was much cheaper.

Now, its big brother the NMO2/70 is light years ahead and is the better comparison to the OP's Tram antenna.

 

[mmckenna]

FWIW, I have the NMO2/70SH and was never really that impressed with the performance. A regular 1/4 wave whip worked just as well (on both bands) and was much cheaper.

Yeah, that's to be expected. It -is- 1/4 wave on VHF. The (slight) benefit to the antenna is that it's got a better radiation pattern on UHF than a 1/4 wave VHF will on the same frequencies.
I ran one for years with a couple of different dual band radios, and eventually gave it to my brother in law. It's big benefit to me was that it's a much shorter antenna than the regular NMO-2/70, which is a pretty tall antenna for a full sized truck.

 

[dkim5nu]

Yeah, that's to be expected. It -is- 1/4 wave on VHF. The (slight) benefit to the antenna is that it's got a better radiation pattern on UHF than a 1/4 wave VHF will on the same frequencies.
I ran one for years with a couple of different dual band radios, and eventually gave it to my brother in law. It's big benefit to me was that it's a much shorter antenna than the regular NMO-2/70, which is a pretty tall antenna for a full sized truck.

What antenna did you replace it with, if you did replace it at all?

 

[mmckenna]

What antenna did you replace it with, if you did replace it at all?

Many years ago I got rid of all my amateur only radios and switched to all commercial radios. That lets me use them as part of my job, and they have plenty of memory for adding all the common ham frequencies I need.
Since all I was really using was VHF, I sold off the dual band radios and now just run single band Motorola or Kenwood with a simple 1/4 wave whip on the roof.