Signal Amplifiers (Amps, Preamps, Distro Amps) - See Chart in Post #1

[Jase88]

True, but the extra gain compensates

A pre-amp can't replace signal that's not there. If a 1.5dB insertion loss pushes a station below reception range prior to reaching the amp, a pre-amp can't change that....

Looks like they've simplified the power inserter...which is a good thing.

[BOUVAL]

I was just saying that the extra gain on the new CM7777 compared to the previous one compensates for the lost of an inserted UVSJ.

Meaning that the new one amplifies more than . . .
.

[ProjectSHO89]

True, but the extra gain compensates.

Unfortunately, the extra gain won't compensate for the insertion loss in the regard of the ratio to signal to noise. Quite frankly, the old ones weren't all that quiet to start with.

A good UVSJ typically exhibits less than .5 dB IL on the VHF port and less that 1 dB (or better) on the UHF port. Either that insertion loss or the noise figure of the amp is a price that has to be figured out.

[stampeder]

Thanks BOUVAL for the early review of the newest model CM7777!

Let's be extremely careful about touting a gain increase since it apparently comes with a cost. In all fairness to all our members we unfortunately still run into the old "most gain = best performance" idea that is wrong on so many levels.

We need to dig into this new model preamp's performance much further so that we can predict some gain/loss values for our members to rely upon.

On another note, many of us have been somewhat suspicious of CM's ability to adapt to consumer requirements in the aftermath of that company's change a few years ago, so this will be an interesting view of their engineering.

[rlongfield]

Not sure if this is the right place or not, if not I do apologize.

I need some help identifying this bit of hardware. It was on the mast of an antenna that I purchased a little while back.
As you can see in the picture it is a black box that mounts to the mast with the 300 ohm wire from the antenna entering the box on one side and a coax cable leaving the other.
The box is made by Channel Master and on the inside has 'tunable FM trap' next to a small screw. The 300 ohm wire connects to the box where it says 'To Antenna' and the coax connects where it says 'to power'. There is also a sticker that say 0064C.
A Google search for CM 0064C returns results for a preamp. Is this a CM 0064C? If it is what kind of power injector does it need as I got none of the internal equipment for the antenna (power injector or rotor control).
I doubt they even had them any more or knew what they were for.

Here is the hardware in question http://imgur.com/hZLHJ

[majortom]

pretty sure u are lookin for a cm-0747 power supply,
according to the Edition1 catalog I have, it shipped with a cm-0064,
and had an output of 18 VDC.

the hard copy I have here is from ~ 1998.

Specs for the CM-0064 are in the preamp chart (see post#1 of the preamp thread)

Assuming it's working still, they can be pretty useful since it is 300 ohm input, so you don't need to use a 300/75 ohm balun along with it's associated losses.

[rlongfield]

Thaks Majortom, I happen to have that PS sitting in my house for my cm7777. Maybe I'll give the 0064C a try to see if it is still working.

Any idea if the coax can be disconnected from the 0064C? The previous owners cut the coax short.

[majortom]

You can probably crimp a new F connector on it.
If you have soldering skills, you can try to disassemble the unit
and replace it (the insulation did look to have signs of dry rot/cracks in ur pic) .
Honestly no idea though, have never seen one.

[roger1818]

Originally Posted by BOUVAL

True, but the extra gain compensates.

Only if you put the UVSJ after the pre-amp. Gain doesn't compensate for losses before the the pre-amp. Only a lower NF will compensate for that, but from what I have read, the new CM-7777 has a higher NF.

[takeaim]

picking up a used original 7777. it isn't currently hooked up, is there any way to ensure it's in working condition? anything to check on the power supply?

any opinions on the original 7777 vs the 'new and improved'?

with the 2 inputs, vhf and uhf, are the frequencies input tailored within that range? ie. what happens if you attached an antenna that receives uhf and vhf signals into the the vhf input, would only the vhf frequencies make it through? just curious.

thanks

[roger1818]

takeaim. Lucky you!!! Probably the best way to test it is to try it. Connect up a small antenna to a TV without it first to baseline your reception and then when you connect it, things should be the same or better (assuming you aren't too close to a tower and are getting overload). Also, open it up (necessary to change the settings anyway) and have a look to make sure everything looks clean.

The original CM7777 is much better! The new one not only doesn't have separate inputs but it has a higher NF. The extra gain is irrelevant. IMHO, avoid the new CM7777.

In separate mode the VHF input filters out all UHF signals and the UHF input filters out all VHF signals. In combined mode one input receives both VHF and UHF and the other input is disconnected.

[takeaim]

thanks, i just don't want to buy it, take it home and be screwed with it. wonder if the seller would have an issue with me opening it up to take a look? apparently it was used in the attic, so shouldn't be as much wear and tear as one that was used outside etc.

is everything labelled inside well to know where to flip the switches to set it for combined then?

thanks

[takeaim]

roger1818 i sent you a private message
thanks

[tomwright]

Hi, apologies if this is posted in the wrong place.

I live in downtown Toronto and installed an antenna last weekend. I'm picking up 30 odd channels with reasonable reception, the antenna is pointed at Buffalo.
Occasionally I can pick up the ION channel (and qubo), but this seems to be intermittent. My guess is it's reliant on weather conditions. I would like to be able to receive qubo more consistently, is this the type of situation where a pre-amp can help?

Thanks for any advice

[roger1818]

tomwright, You haven't provided enough information for us to give you a definitive answer (or at least as close to a definitive answer as you can get), but here are some rules of thumb:

1. If you are splitting the signal between multiple tuner or have more than 50 feet of cable between the antenna and your tuner, a good pre-amp may help.
2. If not, a good pre-amp may still help if it has a lower noise factor than the amp built into your tuner.

An amplifier will not compensate for not having the right antenna for your situation or for an antenna that isn't aimed properly so make sure those are correct first. Check the reception results thread for your location to see what they recommend.