Antenna Revolution?

[USAPatriot]

I had a thought. (Been one of those days, but it does happen on occasion)

One of the banes of scanning reception is signal loss due to coax length and other factors. Fact is, ya want better reception you go up higher. And sometimes the mast/tripod/tower placement isn't exactly optimal with adds even more length to the coax and inevitably more signal loss.

So why not do away with the coax? It seems to me that under certain circumstances everything collected by the antenna could be rebroadcast wirelessly, in essense a wideband repeater. I'm not tech enough to know the pitfalls though the more obvious ones do jump out at me: noise from rebroadcasting the entire spectrum. A jamming effect from the rebroadcast interfering with the collected signals (Seems like the rebroadcast would need to be either much higher or much lower in frequency than the collected signals in order to avoid that). One could probably amplify the signals as well but there's obvious problems there too.

Still, it might be worth it all if it was cost effective and managed to leave the user better off than if he'd been using coax.

Thoughts? -Rod-

PS...I have NO idea if this has already been tried or already been done. Was just pondering my own upcoming signal loss problems.

 

[kb5udf]

Done with sattelites

What you describe is somewhat done with coax:

Someone will correct me if I'm wrong, but this is what is done with most microwave
sattelite systems. A device called an LNA/LNB is a reciver located very near if not in the feed horn of the dish, which converts to lower frequences 1ghz and below, the 3-24 ghz sattelite frequencies. These frequencies are then sent to the sattelite receiver for decoding via the coax.

As far as doing it for terrestrial two way, I've had similar thoughts. To my understanding the most common/similar done for scanning is to have a mast mounted preamp. Which in theory can overcome the losses of coax.

I heard a rumor about a ham 144mhz/2meter repeater that used a uhf downlink with the receiver mounted up the tower.

There are a few one serious practical concern for commerical/amateurtwoway, anything electronic mounted up the tower is subject to the elements and often dies at an inconvenient moment, necessitating a potentially expensive tower climb. It can also be a challenge to get the appropriate power to a radio receiver up the tower reliably from what I've heard since 12v will rapidly diminsh in voltage with cable length.

Perhaps the bottom line is that sattelite dishes, usually being ground mounted are very accessable, tower mounted items typically are not.

 

[TeRayCodA]

I had a thought. (Been one of those days, but it does happen on occasion)

One of the banes of scanning reception is signal loss due to coax length and other factors. Fact is, ya want better reception you go up higher. And sometimes the mast/tripod/tower placement isn't exactly optimal with adds even more length to the coax and inevitably more signal loss.

So why not do away with the coax? It seems to me that under certain circumstances everything collected by the antenna could be rebroadcast wirelessly, in essense a wideband repeater.

I don't think this is legal.(to rebroadcast)

Why not invest in some low loss LMR-400,or hardline coax?
-More practical

 

[USAPatriot]

I looked at the price of LMR-400 last night. Just one spot, but that was enough. The cost is a substantial portion of the value of my scanner. Anyhow, this isn't about me, it's a discussion on theory -Rod-

 

[N_Jay]

I looked at the price of LMR-400 last night. Just one spot, but that was enough. The cost is a substantial portion of the value of my scanner. Anyhow, this isn't about me, it's a discussion on theory -Rod-

Towertop preamps are very popular in commercial systems.

Your retransmitting idea is not practical sice you would need a radio channel as wide as your receive window.

The LNA/LNB (Low noise amplifier, i.e. Preamp/Low noise block converter) is used to move teh sat bandwidth to a lower portion of the spectrum to send it down the cable.

Low-noise amps work well on Sat because the signal level is very consistant, the bandwidth is narrow relative the operating frequency, and interfering signals are very rare.
This is much differnt than a mobile communocations system.

In general the most cost effective sloution for scanning is the best cable you can afford.

SOmeone might get creative and try remote controlling a "Tower Mounty Scanner". :twisted:

 

[Al42]

I looked at the price of LMR-400 last night. Just one spot, but that was enough. The cost is a substantial portion of the value of my scanner. Anyhow, this isn't about me, it's a discussion on theory -Rod-

But one practical aspect that has to be considered is that the rebroadcast scheme would cost a lot more than a few hundred feet of 3/4" dry nitrogen dielectric hardline and connectors.

(If we're talking pure theory - no practical considerations at all - then we just rebroadcast the entire 30-2000 MHz band at 1000 GHz or so with a very directional antenna and there's no problem. That is, if money and physics don't count.)

 

[N_Jay]

But one practical aspect that has to be considered is that the rebroadcast scheme would cost a lot more than a few hundred feet of 3/4" dry nitrogen dielectric hardline and connectors.

(If we're talking pure theory - no practical considerations at all - then we just rebroadcast the entire 30-2000 MHz band at 1000 GHz or so with a very directional antenna and there's no problem. That is, if money and physics don't count.)

Getting close.

Actually, I would say the practical aproach would be to put it on an optical fibre, but of course that is in the Tetra-Hertz range.

P.S. 1000 GHz is 1 THz, and is in the Far Infrared spectrum, so a lense might be more apropriate thn an antenna! (Well, Parabolic Reflectors still work well) :lol:

 

[ReceiverBeaver]

It is unreasonable to expect to obtain a "high performance" DC-to-Daylight scanning-receiving station.....on the cheap. Like anything else in this world, you get what you pay for and you have to expect to pay for what you get. The Antenna System (antenna+feedline) is often said to account for 95% of the performance of receiving or transmitting stations. And this is true. A $10,000 radio will provide poor results if all you're using is a broken off piece of a coat hanger stuck into the imput jack for an antenna.

If you can't afford a decent antenna and some high quality low-loss coax.....then lower your expectations or find a less expensive hobby. Belden 9913 Flex RG8 is about 75 cents a foot. So 100 feet plus worst case shipping would be about $100 bucks. These days you can mow 3 or 4 yards and make 100 bucks. Cease your poormouthing, get a job and buy some gear.