Signal strength conflict?

[N8LHG]

Somewhat obscure in a later post by him, he said he was using 50 ft RG8X which attenuates signal at 850MHz by 6.5 db so the feed line is losing about 78% of the signal at the antenna. I have a similar situation. I have 75 ft of RG213 to a multi band antenna and cannot pick up any of the 700/800 Mhz sites near me. It is a homespun multi band antenna that receives 800Mhz well on a short feed line, but where it is mounted 20 ft high, my 75 ft RG-213 feed line attenuates the signal 5.4 db. I use that antenna for other than 800. For 700/800 the portable antenna that came with all my Uniden Scanners is all I need.

I'm an old time ham radio noob from the 70s. I realize I'm clueless about frequencies over 512MHz. Still learning, though I have 40 years or so more experience of HF and VHF experience. I would be a fool to claim I know about the 512 and above frequencies. The problem I have is discussing any frequency over 500 MHz. I want to learn, yet, have a very solid knowledge of radio technology going back to the 70s or more. I would NEVER claim I know everything, but want to know whats going on. Don't judge me, I'm interested in learning. Digital transmission fascinate me, and while I know the simpler times of high speed CW digital modes, I can assure you I can kick asp of many CW digital modes by ear. I can describer by ear, most CW speeds, and want to share my abilities, but realize, Digital modes are beyond my ability to describer. Give me a break.

 

[GROL]

In the HF bands and even 6 meters, cable length is not nearly as much consequence even using RG58. So it doesn't get noticed much. At those frequencies it is more often an issue of power if you run more than 500 watts. I think the issue is that it is quite surprising how severe the attenuation gets as you get really high in frequency. It can be a big surprise unless you have worked in it much. Even in the 225-400 MHz band which I monitor often, I use surplus RG-213 cables to keep attenuation down. LMR400 would be better, but the deal I got on the RG-213 made it cheap! I have used RG-174 for many HF portable antennas at lengths of about 25 ft. Works just fine with 100 watts. The Times Microwave calculator is very handy for checking attenuation in coaxial cable. It can help you find the compromise of loss vs. the cost of the cable. - Times Microwave Even on 6 meters RG-174 isn't terribly bad at 25 ft. - Times Microwave

 

[n1chu]

Somewhat obscure in a later post by him, he said he was using 50 ft RG8X which attenuates signal at 850MHz by 6.5 db so the feedline is losing about 78% of the signal at the antenna. I have a similar situation. I have 75 ft of RG213 to a multiband antenna and cannot pick up any of the 700/800 Mhz sites near me. It is a homespun multiband antenna that receives 800Mhz well on a short feed line, but where it is mounted 20 ft high, my 75 ft RG-213 feedline attenuates the signal 5.4 db. I use that antenna for other than 800. For 700/800 the portable antenna that came with all my Uniden Scanners is all I need.

Bandwidth was reduced, allowing for additional channels but the FCC opened up the 800 MHz

…And that’s the upside to this story… you don’t need much in the way of an antenna for 700-800-900 MHz. If you are receiving all you need in the VHF/UHF Bands with a coax that is not considerate of higher frequency needs, it doesn’t mean you need to swap out that coax. The stock antenna or the aftermarket 800 MHz one will suffice nicely in most cases. I’ve continued using a previous model base/mobile saw scanner and using the BCDx36HP handheld (and then the SDS100) on 800 MHz while at home, even though I run the LMR400 coax.

 

[N8LHG]

Just to update here. I replaced my coax with a low loss cable, and have noticed a pretty drastic increase in 850MHz signals. All my signals in that band have gone from about -108/-100 dbm to about -90/-80 dbm. I guess I shouldn't be so surprised. Just never worked with frequencies over 460MHz before until recently. Thanks to everyon who helped, it is much appreciated. I guess you can teach old dogs new tricks.