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Discussion Starter · #1 · (Edited)
Kitz Technologies sent me one of the new KT 700 VHF UHF combining amps a couple of weeks ago. I'm very happy with it.





I had two RCA PREAMP1Rs before which were intermittently failing. But those amps are no longer available and I didn't want to put one of them up on my mainmast and have it fail.

I considered the Channel Master 7778 Amplify+ but they were no longer available from any source. This low noise preamp comes at the right time when people are cutting the cord and nothing else is available anyhow

KT-700 TV Booster
 

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Ideally, they would have included a switch to change the combined input to UHF-only, for use when VHF pickup exclusively from a separate VHF antenna is desired.
 

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Discussion Starter · #5 ·
Kitz KT-700 UHF/VHF Combining Pre-amp Vs. RCA PREAMP1R VHF Test

VHF, The KT-700 has substantially more dB than the RCA:

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UHF, not as much a difference in power but a better SNR:


LTE Filtering built in :



It also has an FM trap. No testing done with that.
 

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Looks like the Channel Master 7778 Amplify+ may still be available direct from the Channel Master website. But the Kitz version provides a nice new option, especially since the RCA does not appear available anymore with the dual input.
 

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Discussion Starter · #7 ·
I've searched and searched for the CM 7778 Amplify+. I called Channel Master and as far as the guy I talked to said they won't be available any time soon.

Channel Master appears to be in trouble.

RCA? Typical corporate stupidity.
 

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How does the Kitztech compare to the old cm7777? Worth upgrading?

I'll be testing the KT-700 as soon as I receive mine. I expect it to be good. I'll post here.

There are several versions of the CM-7777. Which one is the "old" version? The original 30 dB gain amp or the 23 dB gain amp?
 

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I'll be testing the KT-700 as soon as I receive mine. I expect it to be good. I'll post here.

There are several versions of the CM-7777. Which one is the "old" version? The original 30 dB gain amp or the 23 dB gain amp?
I believe I got mine around 2001 so it is the best version. At least that is what I was told.
 

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I believe I got mine around 2001 so it is the best version. At least that is what I was told.

Both of the older versions have a noise figure of around 3.0 dB. Same goes for the CM-7778+ so that likely applies to the CM7777v3 too. I don't have any measurements on the oldest version besides gain and noise figure. Except for the gain difference, I don't know what might be better about the 30 dB version.

A lot of which preamp is better comes from anecdotal reports. There are so many variables in those reports that no one has any idea what's going on. That's why bench testing is helpful in assigning numbers to some of the variables.
 

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will give it a complete test and report the results here.
Good to know there is a replacement for my trusty CM 7777 I'm using to combine VHF-hi and UHF antennas. It has been working since 2008 but nice seeing there is a replacement if I need one.

/tom
 

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KT-700 Bench Tests

I ran every test that I normally run on a preamp. Results and comments follow.

Image 1 - Separate and Combined VHF Inputs Gain - Almost no difference between the two.

Image 2 - UHF Gain

Image 3 - FM Filter

Image 4 - LTE Filter

Images 5 & 6 - VHF and UHF Noise Figure - Slightly higher than claimed but I don't make any claims for absolute accuracy. I try to take the main sources of error into account. This test is primarily dependent on the ENR of the noise source being what the ENR says it is. There's no way for me to check that without sending it to an expensive calibration lab.

Images 7 - 10 - Return Loss (SWR) - SWR is never very good on any preamps. The result is a higher Mismatch Loss than I'd like to see.

Images 11 & 12 - 3rd order intermods (IP3) - UHF is 5 dB better than VHF. I don't why this should be. Difference in gain? My own personal scale for TV preamp 3rd order intercept point is this:

+35 dBm - Excellent

The KT-700 is equal to or superior to just about any preamp I've tested. It should perform well in most situations. The noise figure is the best out there for a preamp with filters. The only thing better is the unfiltered KT-200. It would be nice if the VHF gain was lower but I don't think that's possible with the current design.

Note: The two switch DIP switch operates as follows: SW1 - Down - Separate inputs, SW1 - Up - Combined on UHF Inputs, SW2 appears appears to have no function.
 

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I ran every test that I normally run on a preamp. Results and comments follow.

Image 1 - Separate and Combined VHF Inputs Gain - Almost no difference between the two.

Image 2 - UHF Gain

Image 3 - FM Filter

Image 4 - LTE Filter

Images 5 & 6 - VHF and UHF Noise Figure - Slightly higher than claimed but I don't make any claims for absolute accuracy. I try to take the main sources of error into account. This test is primarily dependent on the ENR of the noise source being what the ENR says it is. There's no way for me to check that without sending it to an expensive calibration lab.

Images 7 - 10 - Return Loss (SWR) - SWR is never very good on any preamps. The result is a higher Mismatch Loss than I'd like to see.

Images 11 & 12 - 3rd order intermods (IP3) - UHF is 5 dB better than VHF. I don't why this should be. Difference in gain? My own personal scale for TV preamp 3rd order intercept point is this:

+35 dBm - Excellent

The KT-700 is equal to or superior to just about any preamp I've tested. It should perform well in most situations. The noise figure is the best out there for a preamp with filters. The only thing better is the unfiltered KT-200. It would be nice if the VHF gain was lower but I don't think that's possible with the current design.

Note: The two switch DIP switch operates as follows: SW1 - Down - Separate inputs, SW1 - Up - Combined on UHF Inputs, SW2 appears appears to have no function.
Thanks for the review. Will give it a shot.
 

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Discussion Starter · #15 ·
Kt 700

Calaveras, thank you for the comprehensive testing and review. Very definitive. My testing results were also very positive.

I hope the word gets out there. I would like to be able to link your testing summary to some of the other Pages I'm a member of.

At $89.99 USD, it is price competitive with the usually none available Channel Master CM 7778 Amplify +.

Other than the CM there are no other UHF / VHF combiner preamps available that I know of.

One question, why do you prefer less amplification on VHF?
 

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I replaced a RCA PREAMP1R with the KT700 this past weekend. Its an excellent amp, I have all my channels back including one that I used to have to rotate the antenna to bring in. I'm pleased with this one.
3023099
 

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One question, why do you prefer less amplification on VHF?
It's more gain than most people need for VHF and if they need that much gain then the gain on UHF will be too low. I don't think there's much that can be done without using two different amps in the same preamp. This is what all the other dual input preamps did.

You just have to accept 7-8 dB extra gain. Any gain beyond what's needed to keep the System Noise Figure low subtracts from the dynamic range of the preamp.
 

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Had a near lighting strike a couple days ago. Knocked out the PSU ion my KT-200 So. A new PSU and a KT-700 should be here this week.
 

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Discussion Starter · #19 ·
It's more gain than most people need for VHF and if they need that much gain then the gain on UHF will be too low. I don't think there's much that can be done without using two different amps in the same preamp. This is what all the other dual input preamps did.

You just have to accept 7-8 dB extra gain. Any gain beyond what's needed to keep the System Noise Figure low subtracts from the dynamic range of the preamp.
Actually, the KT 700 does have two amps built in. He may have wanted the extra gain on the VHF side because it looks as if VHF could be making a comeback, and it could be attenuated if needed.
 

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Actually, the KT 700 does have two amps built in. He may have wanted the extra gain on the VHF side because it looks as if VHF could be making a comeback, and it could be attenuated if needed.
You're right. I took mine apart and I see that VHF and UHF sides appear to have identical amplifier sections with different filters. Since I don't know what the amp part is, I can't say if it's possible to lower the gain. Often when lowering the gain it causes the noise figure to go up. I can't think of any reason why you'd want the VHF gain to be higher than UHF. I suspect this is a compromise in the design.
 
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