Winegard CPF-20 single channel uhf filter (channel 20)

[MikeBear]

I have an old Winegard Model CPF-20 single channel uhf filter from the mid 1980's. I bought and used this myself for a couple years in the Bridgeport Michigan area 30 years ago.

Only problem IS, that I can't remember for sure if it's a filter to notch out channel 20, or a band-pass filter that passes channel 20.

I know I was interested in channel 20, so I have to believe it's a band-pass filter to isolate channel 20 only from a uhf antenna.

Does anybody know? I can't seem to find anything on Google about it, as it probably was discontinued before the web as we know it even existed.

The channel filter plugs into a bottom carrier piece that has a "AP PAD" cylinder device with 4 prongs for the jack it's inserted into. This bottom piece is probably so any one of various channel filters could be inserted as needed. It has 75 ohm input and output connectors, and a connector labeled "Coupling" that has what appears as a HUGE terminator screwed onto it.

I'm interested in this filter again, as I'd like to try to get channel 20 WUWB-LD up in West Branch with a second HDB91x antenna pointed just for this channel. I actually think I have a chance at getting it, but it couldn't hurt to have an antenna dedicated to it since I have a spare anyway.

http://www.tvfool.com/?option=com_wr...8e03f8597b896b

Thanks!

[rabbit73]

Welcome to the forum, MikeBear:

I couldn't find any specs for it either. Why don't you try it anyway?

Tin Lee can make an AC7 custom single channel bandpass filter for real channel 20.
http://www.tinlee.com/Matv_filters.php?active=3
http://www.tinlee.com/MATV_headend.p...IGNALINJECTORS
http://www.tinlee.com/PDF/AC7-custom...kup%20Info.pdf
http://www.tinlee.com/pricing.php?active=3

Call them and talk to one of their engineers and email your tvfool report to him.
http://www.tinlee.com/contactUs.php

I think your chances are pretty good. WUWB NM 4.9 dB has co-channel interference from WOTV NM -17.7 dB (difference of 22.6 dB; must be 15.5 or more), and second adjacent channel interference from WNEM NM 47.6 dB (difference of 42.7 dB; must be 44 or less) on channel 22.

Antenna and Installation Advice Needed
http://forum.tvfool.com/showthread.php?t=290

mulliganman used an AC7 for Fox on real channel 49:

question regarding overamplification
http://forum.tvfool.com/showthread.php?t=15025

Do you think it's possible to get this channel?
http://forum.tvfool.com/showthread.php?t=15636
http://forum.tvfool.com/showpost.php...29&postcount=9

[MikeBear]

Thanks Rabbit! I started thinking that "CPF" would most likely mean "Channel Pass Filter". This channel would be on a dedicated antenna all by itself, but I'd have to use a 2-way splitter to bring both uhf antennas into one side of my UVSJ. The other uhf antenna gets all my other local uhf channels.

I don't think WOTV is going to be an issue at all. That's clear over in Grand Rapids, and quite a ways down in level from WUWB. More woods in that direction to block the signal also.

Now, WNEM interfering might be an issue, as that's one of my strongest signals, and they really pump out the juice. However, it's a tad more than 100 degrees to the South of WUWB, but could come in on the side of the antenna pointed at WUWB... So this channel filter might help a little bit in that case, but maybe not with WNEM being so close in frequency...

I'll be trying it in the next week or so and see what happens.

[rabbit73]

but I'd have to use a 2-way splitter to bring both uhf antennas into one side of my UVSJ. The other uhf antenna gets all my other local uhf channels.

No, don't use a splitter in reverse as a combiner for your test, it doesn't always work. The CPF will pass 20 and reject the rest, but you also need to block 20 from the other UHF antenna. This is what Channel Master Jointennas do and what the AC7 does. They both contain a bandpass and a band stop filter for the same channel.

For a test just try the second antenna with the CPF and an amp if needed to see if it will work.

I agree with your evaluation on co-channel and 2nd adjacent (Taboo 2-away) channel interference.

ATSC Recommended Practice:

Receiver Performance Guidelines
Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

5.4.1 Co-Channel Rejection

The receiver should meet or exceed the following thresholds for rejection of co-channel interference at the following desired signal levels (Table 5.1).

5.4.3 Taboo Channel Rejection

The receiver should meet or exceed the following thresholds for rejection of taboo-channel interference at the desired signal levels (Table 5.3, 5.4)

http://www.avsforum.com/forum/25-hdt...xchange-3.html
http://www.warrenelectronics.com/Ant...Jointennas.htm
http://www.channelmaster.com/JOIN_TE..._p/cm-0583.htm

[MikeBear]

So you are saying I need to buy a channel 20 AC7 from Tinlee, to use to combine the separate antenna's?

I doubt I could ever find a channel 20 Jointenna, as they are like finding a unicorn.

[rabbit73]

So you are saying I need to buy a channel 20 AC7 from Tinlee, to use to combine the separate antenna's?

AFAIK that is correct. Have ADTech check my analysis; he is pretty sharp, as is Tower Guy who is a TV station engineer.

You might attract their attention better on the Help With Reception thread if they haven't noticed you yet:
http://forum.tvfool.com/forumdisplay.php?f=7

I have been experimenting with antennas since I was 8, when I built my first crystal set radio; I'm now 82. As a ham since the '50s, I've built many antennas. I have been helping posters on 4 forums with their reception problems for the past 7 years, and I'm still learning.

If your CH 20 CPF works, you can use a separate tuner for that single channel antenna system and feed the output into the A/V or HDMI input of the TV.

I doubt I could ever find a channel 20 Jointenna, as they are like finding a unicorn.

Indeed. That reminds me of a cartoon short, based on a James Thurber story, that I saw many years ago. The husband saw a unicorn and told his wife, who didn't believe him. She said "a unicorn is a mythical beast." Well, after several futile attempts of trying to convince her, he got pretty irritated. She secretly reported what he had told her. When the police and a doctor came, he didn't support her story and said to her "a unicorn is a mythical beast." They took her away.
http://www.imdb.com/title/tt1547222/...?ref_=tt_ov_pl

And what's really weird is I just saw someone asking for a CH 20 Jointenna on the AVS thread I linked above. I said to myself, Is that MikeBear?
http://www.avsforum.com/forum/25-hdt...xchange-3.html

Each 0585 Jointenna was custom tuned for one channel in the UHF band. If you could find one for that section it might be retuned for CH 20 by someone with the test equipment and knowledge necessary. Someone like AntAltMike on the AVS thread.

[ADTech]

I just happen to have a couple of unicorns squirreled away in a drawer somewhere that I bought for a project at home but never used. I almost threw them out last fall when I moved into my new lab space as I'd already written off the investment.

I can re-tune them as needed, but, I have to tell you, the Jointenna is no TinLee AC7! The single channel pass filter on the UHF ones is wide enough to drive a semi through, several tens of MHz wide. You're lucky if you can get a 20 dB notch on the channel reject filter. The VHF one I checked was much cleaner.

It's been a few years since I played with them. I'll see if I can dig them out tomorrow and see what's there.

[MikeBear]

Originally Posted by ADTech

I just happen to have a couple of unicorns squirreled away in a drawer somewhere that I bought for a project at home but never used. I almost threw them out last fall when I moved into my new lab space as I'd already written off the investment.

I can re-tune them as needed, but, I have to tell you, the Jointenna is no TinLee AC7! The single channel pass filter on the UHF ones is wide enough to drive a semi through, several tens of MHz wide. You're lucky if you can get a 20 dB notch on the channel reject filter. The VHF one I checked was much cleaner.

It's been a few years since I played with them. I'll see if I can dig them out tomorrow and see what's there.

Thanks! I have no issue ordering an AC7 if I must. I'm actually away from home for a few more days right at the moment, and haven't put up the antenna on the roof to see if I can get this channel at all. I spent 2 weeks off and on just getting all my other channels locked and strong enough.

I was playing with the spare antenna on the ground (well, at about 9ft on a test mast) Saturday, and got a 9db on this channel (behind solid trees!) Of course, 9db isn't the 15db minimum needed. I figure once I put this antenna up with the other two, this channel should lock just fine.
The issue of course is adding it to the other channels without hurting them. Channel 5 WNEM broadcasts on channel 22 now, and it's a very strong signal.

[MikeBear]

I've been unable to pick up that channel 20. Signal level is just too low due to me being behind trees. They are 85-90ft tall, so I have no hope of getting over the top of them.

There's also no chance of aiming around them, anywhere on my property that I could move the antenna.

[MikeBear]

Since my last posting, I have now been able to get in channel 20 with a dedicated HDB91x antenna, on my new taller mast pipe I installed as detailed in my other thread here. http://forum.tvfool.com/showthread.php?t=15701

Now, I just have to find a way to join this antenna to my main HDB91x that gets all my other UHF channels. Tin Lee wants $170.00 U.S. for an AC7, and that's just too much for me at this time. So, I'm on the hunt for a channel 20 Jointenna again.

[rabbit73]

You probably went here already:
The great jointenna exchange
http://www.avsforum.com/forum/25-hdt...-exchange.html

I suggest connecting your channel 20 antenna to a tuner and connect the tuner output to the aux input of the TV.