CM-7777 Using 12Vdc Power Supply

[Titanium]

Has anyone ever powered a CM-7777 with approximately 12Vdc instead of the provided 15Vdc power supply? Instead on reinventing the wheel I am hoping to minimize my OTA rebuild with any member's experience.

The loaded voltage at the amplifier is 14.5Vdc. Using POE breakout, the loaded voltage is 12.2Vdc. Short of dragging a meter out to the new 65' tower to measure if the amplification is reduced with a 2.3Vdc decrease.... I was hoping that someone has already tried this and could comment?

Have CAT 6 running out to the SD HDHomeRun installed at the current antennas and power it from a 12Vdc POE breakout convertor. Installing a Ubiquiti system with 24" reflector on the tower for a PTP to feed HD satellite transport streams from my office for home theater. Installing an XG-91 on top with a 2nd HDHomeRun. While reconfiguring wiring, thought this would be a great time to retire and simplify.

Thanks for any input!

 

[fred555]

How about one of these to step 12v from POE up to the factory 15V?

Amazon product ASIN B00J03PBW0
If not,
I have a cm-7777 in operation. I have a 12v power supply I can substitute for the factory provided one.
What would you like me to test? Signal levels before and after?
I can probably do this tomorrow night if needed.

 

[navychop]

Is be interested to know.

 

[Titanium]

Thank you Fred! Might need to step it up. The 12Vdc test before/after would be very helpful! Interested if there is any change in signal quality and signal level readings.

All channels at my location are at threshold and only will lock with the CM-7777 in-line. Placing the HDHomeRun at the antennas avoids the coax run loss and gives an extra dB.

As you can see it is pretty tough location. Typically only receive real channels 10 and 25 at 12-15' ground effect and San Francisco channels in early AM and early evening during summers. Hoping the new location and height might reliably add the Chico, CA channels. Every bit of signal helps!

 

[DVB-S2]

If you're seeking the best S/N ratio for those weak signals, you'd be better off by about 2dB with a low-noise pre-amp like a Research Communications or Kitztech. The CM 7777 is quite noisy compared to those and others. Can you post a link to your TVFool report?

 

[Titanium]

Thanks DVB-S2. I'll look into these amps

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=f1f0e048ba244a

Rented a lift a few years ago and other than the ground location, the new tower location was the only spot on the property to provide any signals.

 

[Radioguy41]

The CM-7777 is rated at 30dB gain while the comparable Research Communications pre-amp is rated at 23dB and the TOL Kitztech is 25dB gain. The noise on the CM-7777 is 2dB compared to 1dB (Kitztech) and .4dB (Research Communications). The numbers don't support the cost of changing, in my opinion. If they did I'd replace my CM-7777.

Titanium, I would fully expect a 20% decrease in voltage to at least cause a drop in signal gain, probably even non-function of the booster. I've never seen a threshold spec for the CM-7777 but I would suspect a 20% decrease in voltage would exceed the threshold. There are replacement injectors available.

www.amazon.com/Inserter-Amplifier-Electrical-Transformer-DV-12225S/dp/B00UV98C0K

http://www.summitsource.com/winegar...7.html?ref=1&gclid=CPfelOjElsUCFc3m7AodRjgAMA


Larry

 

[FTA4PA]

Has anyone ever powered a CM-7777 with approximately 12Vdc instead of the provided 15Vdc power supply? Instead on reinventing the wheel I am hoping to minimize my OTA rebuild with any member's experience.

The loaded voltage at the amplifier is 14.5Vdc. Using POE breakout, the loaded voltage is 12.2Vdc. Short of dragging a meter out to the new 65' tower to measure if the amplification is reduced with a 2.3Vdc decrease.... I was hoping that someone has already tried this and could comment?

Have CAT 6 running out to the SD HDHomeRun installed at the current antennas and power it from a 12Vdc POE breakout convertor. Installing a Ubiquiti system with 24" reflector on the tower for a PTP to feed HD satellite transport streams from my office for home theater. Installing an XG-91 on top with a 2nd HDHomeRun. While reconfiguring wiring, thought this would be a great time to retire and simplify.

Thanks for any input!

Here is a link for troubleshooting the Channel Master CM-7777. It indicates that the output voltage from the power inserter will range between 18-23VDC and that after the cable run will likely be lower. Step 4 goes on to state that as long as the amplifier is getting above 12VDC it should work correctly.
http://support.channelmaster.com/hc...plifier-to-make-sure-it-is-working-correctly-

 

[Radioguy41]

Ah, that's the spec I couldn't find. Well according to that it won't function at 12vdc which is about what I figured. I hand build solid state AM xmitters and once you get outside of a +-10% window there are usually issues. Good to have that info, thanks for the link.

 

[Titanium]

Great find! Near the voltage limit, but might work.

 

[FTA4PA]

Great find! Near the voltage limit, but might work.

Definitely worth a shot. Good luck!

 

[. Raine]

When I had to fix mine, the voltage regulator inside it was a 7808. So with 12V, I'd think that you'd be fine.

 

[fred555]

Wow unexpected results:

Here is the signal using the factory 15v 300ma supply:

And here is the signal using a 12v 6amp supply:

The Signal Strength is actually higher with 12v supply!!

 

[. Raine]

That doesn't actually surprise me, if you don't have a long cable run. I think they overpower the units some to overcome long/sloppy cable runs but on a good setup, it kinda works for the worse.

With a 7808 regulator, they're expecting a drop of 7 volts. That's a real lot!

 

[fred555]

Here are the specs from TVfool on that channel:
39.6 NM db
-51.3 Pwr dbm
1edge 20 miles

 

[. Raine]

Lucky Dog, you get MeTV OTA!

I used to get it here but lost it early on this winter!

 

[fred555]

Lucky Dog, you get MeTV OTA!

I used to get it here but lost it early on this winter!

And I hardly watch it OTA since I put my 10 foot BUD up a month ago.
101W MEtv Metv2 Heroes, Decades and Movies is where I watch mostly now.

 

[fred555]

Brian I think I owe you a beer for gaining me some signal:

 

[Titanium]

LOL!!! You are welcome, Fred!

Thanks everyone for all of the input, suggestions and testing! I decided to try the CM7777 with the POE breakout of 12.2Vdc. If not successful, the Kitztech looks pretty amazing and I might just have to buy a new toy!

I am getting anxious to start getting the gear mounted, but waiting on some of the last pieces like the the poly utility box and the rotor/mast 2nd coat of black paint to cure. Ordered a small solar panel and box fan to cool the utility box, but going to first test without.

This weekend, my wife, Lin helped lift the tower. She monitored the base and roped the tower away from the eave as we tilted the section up. We then lifted the tower 18" to drop the legs into the receiver holes. Bonded the tower and base to the structure ground and installed an outlet at the base.

Just finished up ordering all of the guy wire, insulators and misc. hardware. Have the tower sitting retracted at 23 feet in 1600+lbs of cement and rebar and roped off on the roof. Decided to measure the wall stand-off support after dropping into the base (in addition to the earlier plumb bob measurements). Both measurements were the same so the plans were dropped off Saturday and should have the bracket back from the fabricator tomorrow. Measure twice, fab once...

Hope to have the rotor, WiFi parabolic, and XG91 (and maybe the YA-1713) cranked up to 65' by the end of next weekend. Once the WiFi and OTA is settled, definitely hoisting an inverted V for 80-10m then decide if the 10/20/40 beam is going on top of the 65' or install the Rohn 45' that I have stored..... Decisions... decisions...

No instant gratification on tower installations!

Thanks again for your help. Photos to follow....

 

[fred555]

I don't believe the Kitztech's are waterproof, so make sure your poly box has extra space if you decide to go that route.