# Does Anyone Make (Or Can I Make) A Channel-Specific (47) Attenuator



## SpankyInChicago (May 13, 2005)

Long story short: I have a setup that works great about 95% of the time for all of my available OTA signals. I have an alternative setup that works great about 99% of the time for all of my available OTA signals except one. I've done some experimenting and believe that this one station is too strong and that is why it doesn't show up on my HR10-250's receiver which is sensitive to overly-strong signals.

I've used the Radio Shack attenuator, but unfortunately it cuts down the other signal too.

Does anyone make an attentuator for just a single frequency (channel 47), or are their electronic kits or schematics I could buy to make my own?


----------



## thegeek (Dec 16, 2002)

Channelmaster Jointenna.


----------



## SpankyInChicago (May 13, 2005)

thegeek said:


> Channelmaster Jointenna.


Not what I want. I want an attenuator not a combiner. Thanks, though.


----------



## JimSpence (Sep 19, 2001)

I think what thegeek is suggesting is that you separate ch 47 so that you can then attenuate it and then recombine it.


----------



## thegeek (Dec 16, 2002)

Oops, didn't read the post carefully enough.

Don't post drunk kids!


----------



## shanew1289 (May 7, 2004)

Search for Notch Filter. Get through the cable descrambling hits and there is devices that can be tuned to attenuate a channel. But I dont know if the attenuation amount is adjustable.


----------



## shanew1289 (May 7, 2004)

http://www.microwavefilter.com/tunabletraps.htm

They cost anywhere from $30 to $50 I think.

some are 25 db, 12 db, and you need to know the frequency to order the right one.


----------



## tucsonbill (Aug 11, 2004)

SpankyInChicago said:


> Long story short: I have a setup that works great about 95% of the time for all of my available OTA signals. I have an alternative setup that works great about 99% of the time for all of my available OTA signals except one. I've done some experimenting and believe that this one station is too strong and that is why it doesn't show up on my HR10-250's receiver which is sensitive to overly-strong signals.
> 
> I've used the Radio Shack attenuator, but unfortunately it cuts down the other signal too.
> 
> Does anyone make an attentuator for just a single frequency (channel 47), or are their electronic kits or schematics I could buy to make my own?


If I can probe a little more, why do you think that the signal is too strong?


----------



## SpankyInChicago (May 13, 2005)

tucsonbill said:


> If I can probe a little more, why do you think that the signal is too strong?


The signal comes in fine without amplification and disappears when amplification is applied.


----------



## SpankyInChicago (May 13, 2005)

shanew1289 said:


> http://www.microwavefilter.com/tunabletraps.htm
> 
> They cost anywhere from $30 to $50 I think.
> 
> some are 25 db, 12 db, and you need to know the frequency to order the right one.


http://www.microwavefilter.com/pdffiles/pg33.pdf

Perfect. Thanks.


----------



## SpankyInChicago (May 13, 2005)

Related question: does anyone make a single channel amplifier?


----------



## TyroneShoes (Sep 6, 2004)

I am using two dual notch filters from Microwave Filter to do exactly this...knock down some stronger carriers in a MATV system I have set up at work. I can't remember what we paid for them, but I think they were over $100 each (MF is very proud of their stuff). They will knock a carrier (two, actually) down about 20 dB, but you can slope-tune them if that is too much. They are tuneable over a large band, certainly over the entire TV band. I'll try to find the model number if needed. You might also search Blonder-Tongue dealers.

The single-channel fixed traps are probably not cheap as one-offs, and can't be tuned. They probably also attenuate too much for your application (25-30 dB). They are designed to be bought in bulk by CATV systems to completely eliminate a premium channel at the tap in an open system.

Another thing that might work if you have no channels above the channel in question (or else no channels below) is either a hi-pass or lo-pass filter, or a line EQ, which will slope the whole band a prescribed amount, possibly bringing the high channel in line with the lower ones if applied correctly. You may have to use it in concert with additional amplification. LEQ's are cheap, about $15.


----------



## SpankyInChicago (May 13, 2005)

TyroneShoes said:


> I am using two dual notch filters from Microwave Filter to do exactly this...knock down some stronger carriers in a MATV system I have set up at work. I can't remember what we paid for them, but I think they were over $100 each (MF is very proud of their stuff). They will knock a carrier (two, actually) down about 20 dB, but you can slope-tune them if that is too much. They are tuneable over a large band, certainly over the entire TV band. I'll try to find the model number if needed. You might also search Blonder-Tongue dealers.
> 
> The single-channel fixed traps are probably not cheap as one-offs, and can't be tuned. They probably also attenuate too much for your application (25-30 dB). They are designed to be bought in bulk by CATV systems to completely eliminate a premium channel at the tap in an open system.
> 
> Another thing that might work if you have no channels above the channel in question (or else no channels below) is either a hi-pass or lo-pass filter, or a line EQ, which will slope the whole band a prescribed amount, possibly bringing the high channel in line with the lower ones if applied correctly. You may have to use it in concert with additional amplification. LEQ's are cheap, about $15.


Thanks for the info. If you can find those model numbers that would be great.

Also, any idea on single channel amplification? Either where to buy or how to build? If I could either attenuate 47 or amplify 21, 27, and 31, life would be great.


----------



## TyroneShoes (Sep 6, 2004)

SpankyInChicago said:


> Thanks for the info. If you can find those model numbers that would be great.
> 
> Also, any idea on single channel amplification? Either where to buy or how to build? If I could either attenuate 47 or amplify 21, 27, and 31, life would be great.


Been too lazy or distracted to walk to that side of the building.

Sounds like a line EQ might work, by attenuating 47 more (respectively) than the lower channels. You might need more amplification afterwards, too.


----------



## GTO40 (Jul 25, 2005)

Attenuate Ch 47 down would be best as TyroneShoes suggest. 

Blonder Tongue or Pico-Macom manufacture single channel amplifiers (search thier websites), cost varies, are adjustable. 

Curious - How old is your TV antenna? Preamp? Some area's of the western suburbs had antenna's installed during the Reagan administration. If this is your vintage time for a new one.


----------



## SpankyInChicago (May 13, 2005)

GTO40 said:


> Attenuate Ch 47 down would be best as TyroneShoes suggest.
> 
> Blonder Tongue or Pico-Macom manufacture single channel amplifiers (search thier websites), cost varies, are adjustable.
> 
> Curious - How old is your TV antenna? Preamp? Some area's of the western suburbs had antenna's installed during the Reagan administration. If this is your vintage time for a new one.


Brand new house with brand new antenna. Winegard HD8200P. Channel Master 0064 preamp causes 47 to be overpowered but all other stations are fine. No preamp but using a variable gain line amp causes 47 to be fine but 21, 27, 29, and 31 are often weak.

My problems are not related to equipment per se. I have massive multipath problems as about 200' feet to my north and east and 200' feet to my south and east are massive ComEd high tension towers.

The Hancock and Sears Tower are 104 and 106 degrees respectively from my location, but to overcome the multipath issues my antenna is at about 85 degrees. I am sure this is part of the problem, but aiming directly at 105 degrees seemed to catch the reflection from the high tension towers just right to cause massive multipath (i.e. fluctuations between 10 and 95 on my HR10-250 signal meter). Turning to 85 reduced multipath to almost non-existant but being off-axis that far causes loss in signal strength.

It was a nightmare that I thought I solved back in July. But after the weather turned cold and we got some snow / ice, I started having problems again.


----------



## GTO40 (Jul 25, 2005)

The Winegard antenna & Channel Master preamp are great choices.

Look first at the antenna to preamp connections as you could be experiencing signal overload at the preamp input. Install an inline attenuator between the antenna & preamp input (an example can be found at this link).

http://www.smarthome.com/7802.html

Aim the antenna for the 104 & 106 hotspot, start with a 6db attenuator and attenuate higher, until the signal is stable & clearly received. When you are satisfied, weatherseal all connections. For a quick & accurate method try to find/rent a TV antenna meter such as a Leader LF941. Aim for an average input from all TV stations to be no higher than 6dbmv, and verify clarity of the received signal using a portable TV.

One final note, if the TV antenna is below the treeline, you may have to repeat this step once the trees bloom with leaves in the spring.


----------

