[majortom]

Depending on where the tree is relative to the antenna, it may actually help.
For instance, if he is aiming for Buffalo, and the tree is helping to block the CN tower some, that would probably be a good thing...

On the other hand if the tree is obstructing in the direction of Buffalo, well...

 

[bev fan]

Lately I have been having issues with 2.1 and 35.1 stations. They were always weakest signal stations but were working great for the last few years. Rotating antenna would not help. I am thinking that it may be 7777 CM preamp, it could have gotten damaged since we had temperatures below -20 C this winter.
Can anybody recommend any good preamp that blocks LTE signal as well as that could be another issue.

 

[holl_ands]

C-M has a new Preamp with LTE Filter...and a Separate LTE Filter that MIGHT use the SAME Filter....but their Specs are USELESS, implying that there is NO LOSS up to 698 MHz and then a LOT of LOSS for 700 MHz and above....an Impossibility....and I haven't seen any measurements.

The ONLY LTE Filter for which I have seen measurements is RS 15-00396 4G_LTE Low Pass Filter, see Loss Curve Posted by ADTech, 27Nov2013:
https://photos.imageevent.com/holl_...4G_LTE Low Pass Filter - ADTech 27Nov2013.png

AT&T (et. al.) 4G/LTE Cell Towers transmit in the 734-746 MHz Band.
Verizon (et. al.) 4G/LTE Cell Towers transmit in 746-757 MHz Band.

Note that Filter Loss in LTE Tower Transmit Band is more than about 45 dB.

Also note Significant Loss on Higher Channels, Do NOT use unless you are SURE you NEED it.

Also see my post from a few days ago, which provided links to alternative LTE Filter Specs:
http://www.digitalhome.ca/forum/186...82249-4-bay-mclapp-lte-700-a.html#post3022297

 

[bev fan]

Thanks holl_ands. For now I have ordered Winegard LNA-200 Boost XT from amazon. I will try it this weekend. if it does not work I can always return it and buy CM 7777 HD dual preamp with LTE Filter. I do not want to buy another CM 7777 as many people are having problems with those.

 

[go4it]

Winegard LNA-100 Boost vs. Channel Master Drop Amp

I tried the Winegard LNA-100 Boost via Amazon (love the return/refund no hassle) against my current CM drop amp.

No difference. I thought maybe the "ultra low noise' of the Boost would make a difference, but nah. The CM drop amp is a stud; well built, great tolerance of near signals, and super reliable.

 

[cyberham]

Installed a CM-7777 bought locally yesterday on mast of my Clearstream 2V. Success! I had heard all the warnings that the 30 dB would cause overload. But my best installation of my antenna is only 7 feet high on top of a fence, and it is buried between houses looking down a between-house tunnel which fortunately points south. I presume the houses may protect the antenna from strong local signal overload. CM-7777 added 7 new channels (29 and 49 plus subs) and strengthened weaker ones (4.1) without any deterioration of local signals. I also have a low-cost 10 dB amplifier at my TV. This seems to do little but doesn't hurt, so I'm leaving it in line for now.
Channels now received reliably: 4.1, 4.4, 5.1, 7.1, 7.2, 7.3, 7.4, 9.1, 11.1, 17.1, 17.2, 17.3, 19.1, 23.1, 23.2, 25.1, 29.1, 29.2, 29.3, 35.1 (night), 36.1, 40.1, 41.1, 41.2, 42.1, 47.1, 49.1, 49.2, 49.3, 49.4 (49 all at night), 57.1.
Channels scanned in but not watchable: 2.1, 2.2, 2.3, 2.4, 6.1, 6.2. (No 26.1, 26.2, 26.3 anymore?)

Where do I go from here? I doubt more amplification will help. Would converting from C2V to C4V help?


TV Fool

 

[Jorgek]

Probably getting the ant higher up is the next step. That's a lot of gain with the 2 amps inline. Your tuner must be working hard not to introduce overload. Though increasing height may cause overload problems!
Channel 26 is directional. Look at your TV Fool map. If you want 26 (not my choice of programs) you will have to re-orient the ant away from the Buffalo stations.

 

[cyberham]

I agree raising antenna is logical. I might be able to go to 10 or 12' if I install a mast against the fence but no more. I have no roof access. I will experiment with rotating antenna left and right though it seems to be at a sweet spot now able to receive all quite well. I am connecting directly into the TV without a PVR or splitting. I suspect the TV is good quality and able to handle the strong local signals. But I certainly am not interested in Ch. 26 if it means lowering signals from the other US channels.

 

[bev fan]

My CM 7777 had stopped working properly after this winter so I installed CM 7777 HD preamp and problems with 2.1 and 35.1 channels is gone. It is dual preamp so if there were overamplication problems it could be reduced from 30 DB to 17 DB but so far I have no problems considering that I can see CN tower from my second floor window.

 

[cyberham]

With TV Fool in #4306 above and equipment showing in my signature, on an exceptional night I have received NM as low as -32.6 (WPXJ) or -30.7 (WROC). More typically, on a good night, maybe -12.2 (WGRZ) though the last few nights haven't been good. How low a NM should you be able to receive for, let's say, an antenna 10 feet high? I think the answer is "it depends" since there are too many factors involved to be able to predict precisely.

 

[majortom]

obviously predictions are only under "normal" conditions.

 

[byebye_cable]

How to fix Research Communications pre-amp

How to fix Research Communications pre-amp?

I got an email back from them saying it was likely the transistor but the company has closed.

 

[majortom]

would have to have some documentation.
See if they will send you a schematic diagram.
without one ur essentially reverse engineering it just to determine how it is supposed to work.
and unless you know how it's supposed to work, ur probably not fixing it.

examining your photo, looks like maybe 3 semiconductors in total.
The 3 terminal device laying upside down is probably a 3 terminal voltage regulator.
I would check the voltage in, and the voltage out to that device, see if it is regulating.
If you lift up on it carefully, you will be able to read the part number of the device.
Given that you can confirm if it is indeed a voltage regulator. The other two devices with 4 leads circled might be transistors,
I don't know. If you can read the markings on them, they can be looked up as well to determine what they might be.

If indeed that turns out to be a 3 terminal positive voltage regulator laying face down in lower right, here is a datasheet describing it.
It would be the one with the TO-92 package.

http://users.ece.utexas.edu/~valvano/Datasheets/LM78L05.pdf

 

[Jase88]

You buried the lead here: Research Electronics is done. Sad to hear that...

 

[chinadog]

I have the same pre-amp. It has a sensitive PHEMT transistor. It has gone on me 3 times over 5 years or so so I have learned to keep some extra transistors in stock.
They are available from NEWARK element14 and are $5.30 each. Here are the details:

Stock #; 96K6512 Manufactrer part # ATF-54143-TR1G Tape and Reel Cut 1 4

Description: MOSFET, RF, HEMT, SOT-343; Drain Source Voltage Vds:5V; Continuous Drain Current Id:120mA; Power Dissipation Pd:725mW; Operating Frequency Min:450MHz; Operating Frequency Max:6GHz; RF Transistor Case:SOT-343; No. of Pins:4Pins;

It is a tiny piece but you will able to identify( with a magnifying glass) which resistor needs to be replaced. I had a local electronic repair shop do it for me.

 

[ExDilbert]

With the cost of the part(s) and shipping, it's susceptibility to failure and paying a repair shop, is it worth repairing? The Kitztech KT-200 may be a good replacement.

 

[majortom]

Hey chinadog,

Thanks...
Here is the datasheet for the FET he mentions...
https://docs.broadcom.com/docs/AV02-0488EN

It will be marked on the top like so per the datasheet. Will probably need a magnifying glass the read the marking.

“4F” = Device Code
“x” = Date code character
identifies month of manufacture.

 

[chinadog]

I will take a picture of one of my spares and post it.

Research Communications sold me a spare second unit at a reduced price so that I could easily stay operational while replacing a burned-out phemt. I my keep pre-amp a little more protected by having it just inside the attic on the other side of the ground block. That means about 15 ft of coax loss but I can live with it. The last time I blew the PHENT it was totally self-inflicted as I was connecting and re-connecting the ground while the pre-amp was connected and powered!

 

[fortissimo]

I have a CM4221HD (new ver, didn't do the mod except bending a little) in the balcony, 2nd floor in an apt balcony, surrounded by other buildings in a flat terrain (sea level) in an urban area in the Greater Vancouver area.

With the Wingard AP8275 preamp, it helps to pick up the Bellingham PBS K24IC-D, but barely, and not on a bad day.

But I need to feed a few tuners though: 2 TVs, one Hauppauge Broadway, and occasionally Hauppauge USB tuner (and in the past, Bell 9242 PVR w/ ATSC tuner), so I need a 1 - 4 distribution. I bought a "for cable" distribution amp from BestBuy, and it didn't seem to help, plus it seemed to be worse, and I am not sure if it's getting some DC interference from the DC injector for the Wingard amp or what (I placed it before that of course), or it has some prob (IIRC it was an open box before, a house brand by BB).

So right now I am using a passive (sat grade) 1-2 splitter, and getting by, and PBS doesn't come in all the time. I am looking for a better but hopefully not expensive solution for a 1-4 distribution amp.

I am ok with electronics and can also go the DIY route, if the parts are not hard to come by, if I can save some money. As long as the result is good (i.e. low noise, suitable gain).

Also, if I upgrade the amp from Wingard (at that time, it was the most reasonable choice for bang for the bucks, there are better preamps but they cost a lot more), would that help a lot? There is no way I could place the antenna any better as I don't live high enough (20' off ground).

Thanks in advanced!

 

[majortom]

Post your tvfool so folks can get an idea what ur up against

Winegard AP8275 preamp is probably overloaded with too many strong signals.
VHF Gain 29 dB
UHF Gain 28 dB

A Winegard AP8700, with 10 dB less gain on either band will still get overloaded pretty easily unless we take some care to reduce strong signals
at the input.
A quote from retailer Solid Signal's webpage.
"NOTE: Preamplifiers and/or amplifiers only amplify the signal your antenna receives. They cannot extend the receiving range of an antenna or help pull in signal. Also, DO NOT use the higher gain models within 35 miles of your transmitters."

A classic example of what can happen with too much amplification was at my sister's house.
Her issue was FM band Overload.
https://rickcaylor.websitetoolbox.c...ference-9760197?pid=1306079123#post1306079123

The Channel Master CM3414 distribution Amplifier is essentially an active 4 way splitter, with just enough amplification to overcome internal passive splitter losses and some feeder losses. But can still get overloaded under the right conditions as we see from the spectrum at my sister's house..