Where have all the UVSJ's gone? - Canadian TV, Computing and Home Theatre Forums

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post #1 of 26 (permalink) Old 2017-02-08, 02:13 PM Thread Starter
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Where have all the UVSJ's gone?

Scouring the internet today only to find that all of the high quality UVSJ's are discontinued? What's up with that?
Are there any suitable alternatives for combining a UHF antenna and VHF antenna with minimal insertion loss?
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post #2 of 26 (permalink) Old 2017-02-08, 03:17 PM
 
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You might try Tin Lee Electronics. Their products are very high quality.

Here is a link: http://www.tinlee.com/MATV_headend.p...TVBANDSPLITTER

Delhi SFA 1483, Antennacraft Suburban VHF, CM7778
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post #3 of 26 (permalink) Old 2017-02-08, 03:19 PM
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Amazon advertises Blonder-Tongue Z-UVSJ....but shows picture of similar "Tru-Spec" part....you should also check FleaBay for Pico, MACOM, Tru-Spec, Hollands as well as Blonder-Tongue "UVSJ" type devices:
http://www.multicominc.com/wp-conten...dsv_series.pdf [B-T Specifications]
https://www.amazon.com/Blonder-Tongu.../dp/B004BTY700
[Note links to MCM Stellar Labs and Antennas Direct VHF/UHF Combiners in the "Other Items" section.]

OTOH: Radio Shack 15-2586, MCM Stellar Labs 33-2230 and Antennas-Direct VHF/UHF Antenna Combiners have DC PASS on the UHF Port, which is what you want if you insert it AFTER the Preamp, so that VHF (incl Strong FM signals) do NOT go through the Preamp, likely causing Intermodulation and FM Second Harmonic Interference [unlike UVSJ's which erroneously have DC PASS only on the VHF Port]:
https://www.radioshack.com/products/...itter-combiner
Stellar Labs UHF - VHF Antenna Combiner | 33-2230 (332230) | Stellar Labs
https://www.antennasdirect.com/store..._combiner.html

Performance Summary:
Splitters, Attenuators, Filters, Diplexers, Other Signal Gear

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2017-02-08 at 03:35 PM.
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post #4 of 26 (permalink) Old 2017-02-08, 11:32 PM Thread Starter
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I'm planning on joining my UHF and VHF antennas prior to feeding into my mast mounted Winegard LNA200 preamp, so I am assuming the simple UVSJ is all I need. Just wondering why they have seemed to all but disappeared. They are the simplest, cheapest and most efficient method I have seen.
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post #5 of 26 (permalink) Old 2017-02-09, 07:02 AM
 
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Quote:
Just wondering why they have seemed to all but disappeared.
It appears that both Hollands and Steren (Pico) quit making them.

Quote:
....cheapest ...
They probably concluded that low volume inexpensive accessory items weren't work the hassle of loosing money over. They are businesses, after all, they're not required to make items that they don't make money on - that's the seeming function of government.
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post #6 of 26 (permalink) Old 2018-01-31, 12:58 PM
 
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I ordered 2 Pico-Macom a few years back from Solidsignal but they take water (despite putting a lot of Dielectric Silicone grease on them...Very strange...). So I recently ordered the Antenna Direct outdoor unit (EU385CF-1Z) which has similar spec (EU385CF-1Z) than the Blonder-Tongue/Pico models but it didn't work at all....

The unit is not defective as I ordered a second one and had the same issue. I plugged them in the house to test and everything is fine...I'm sure it has something to do with the DC pass which is on the UHF port instead of the VHF on the Blonder/Pico-Macom... All my setup is grounded so not sure what causes the issue... Adding a splitter in between the UHF Antenna and the AD combiner resolves the issue but with an extra 3.5 dB of losses...And defeats the purpose of the low insertion loss of a diplexer...

Here is the setup:

VHF: Wade 10Y13S --> Tin-Lee Ch 13 Bandpass Filter --> UVSJ VHF Port --> Line (see below)--->
UHF: Antenna Direct DB8e --------------------------------->UVSJ UHF Port --> -----------------------Line --> input of CM7778 output to Cable inside the house with DC for the CM-7778. DC is injected in the house...

Thinking about ordering acouple more more UVSJ's and build an enclosure but they are hard to find...

Last edited by imeric; 2018-01-31 at 01:14 PM.
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post #7 of 26 (permalink) Old 2018-01-31, 06:19 PM
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Quote:
Originally Posted by sempei View Post
I'm planning on joining my UHF and VHF antennas prior to feeding into my mast mounted Winegard LNA200 preamp, so I am assuming the simple UVSJ is all I need. Just wondering why they have seemed to all but disappeared. They are the simplest, cheapest and most efficient method I have seen.
Do you NEED a Preamp for the VHF Freqs....presumably JUST Ch13....which may CHANGE with the upcoming RePack??? Since Coax Loss is a LOT LESS on VHF than UHF, you might not NEED it unless going to more than 4-Drops....or have very marginal signals. You MIGHT be better off using A-D, MCM or R-S VHF/UHF Splitter (Di-Plexer) with ONLY UHF Signals going thru Preamp.....

When you Amplify Hi-VHF Freqs, you also have to be very careful as to whether you have any Strong FM Stations whose Second Harmonic [with twice the 200 KHz Bandwidth] falls on top of any of your weaker Hi-VHF Channels....or if there are MULTIPLE Strong FM Stations....in which case you would need to add an FM FULL BAND FM Filter (A-D or MCM but NOT R-S's Partial Band Filter].

Suggest you enter your accurate Address into both TV Fool and FM Fool - Home and copy/paste results so we can see them. Also describe your arrangement with number of Drops, Cable Lengths, etc.
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Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #8 of 26 (permalink) Old 2018-01-31, 08:26 PM
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A few months ago I was noticing similar, getting fewer and further between sellers.
So I bought like 1/2 dozen or so, just in case...

DB4E/VHF Yagi rotor FM Bandstop ap-8700 preamp 4way split LG lcd.
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post #9 of 26 (permalink) Old 2018-02-01, 10:21 AM
 
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Anyone has an idea as to why the antenna direct combiner is not working for me?

Thx
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post #10 of 26 (permalink) Old 2018-02-01, 11:18 AM
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Quote:
Originally Posted by imeric View Post
Anyone has an idea as to why the antenna direct combiner is not working for me?

Thx
Your explanation that the DC pass for UHF is the cause of the problem isn't logical, because there is no DC voltage before the 7778 input. Something else must be going on.
Quote:
The unit is not defective as I ordered a second one and had the same issue. I plugged them in the house to test and everything is fine...
Exactly HOW did you connect them in the house when they were OK; what was connected to what?

Does the Antennas Direct UVSJ work OK with a different preamp?

However, when I ordered two Antennas Direct UVSJs for evaluation, one had the label pasted upside down, which might cause the cables to be connected to the wrong inputs.



May we see your TVFool report to help us understand your reception problem? I can't find your report in your previous posts.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2018-02-01 at 01:43 PM.
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post #11 of 26 (permalink) Old 2018-02-01, 12:16 PM
 
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Quote:
Anyone has an idea as to why the antenna direct combiner is not working for me?

Thx
You're invited to contact us for assistance.

https://www.antennasdirect.com/customer-service.html

Antennas Direct Tech Support
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post #12 of 26 (permalink) Old 2018-02-02, 09:44 AM
 
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Quote:
Your explanation that the DC pass for UHF is the cause of the problem isn't logical, because there is no DC voltage before the 7778 input. Something else must be going on.
I couldn't agree more... I've had this setup with the UVSJ for a few years now and it's been working great. I spent lots of hours tweaking my setup and I'm fairly proud of it...Getting ABC in my area is not an easy thing to do and I'm fairly sure I'm one of the few in my area (thx to the Tin-Lee filter and the good Old 10Y13S... Here is my TVFOOL

I've also changed to a DB8e from a CM-3228 which is a lot more selective and helps me reduce strong signals from local stations and increased gain for the US channels...This change was done 2-3 years ago... In a nutshell I get all channels someone can get in the Mtl area with only sporadics fades on my VHF-Hi ABC

In the house I feed 4 distribution amps to 4 TVs and 10 Tuner cards. I'm also feeding my tenant bypassing the CM-7778 with a - 6db tap with no DC. His feed is short with only one TV so no amplification required...

I tested the Antenna Direct Combiners in the house after one distribution amp and the UHF/VHF ports going to 2 tuner cards. Looking at the signal quality both UHF and VHF channels will come in strong. However in this case it's not combining but splitting the signal...And of course only UHF channels come in on the UHF port and same thing for VHF...

The other thing that is not logical is why the UVSJ takes A LOT of Water despite the incredible amount of Silicon I put on it...I don't get it and no way it's coming from the RG-6...I ordered a bunch of ASKA from goldmine and will build an enclosure... There might be an issue with my Tin_lee connectors I'll need to check this out as well..
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post #13 of 26 (permalink) Old 2018-02-02, 02:54 PM
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Thank you for the TVFool report for your location.
Quote:
Adding a splitter in between the UHF Antenna and the AD combiner resolves the issue but with an extra 3.5 dB of losses...And defeats the purpose of the low insertion loss of a diplexer...
I think I understand why the splitter before the AD UVSJ helped. Your indoor test with the UVSJ shows that the UVSJ is OK, but you have an overload problem from your strong local signals. The overload causes IMD (Intermodulation Distortion) which creates spurious signals in a preamp or tuner. These spurious signals (spurs) interfere with the reception of your weaker signals because they raise the noise floor that reduces the SNR of the weak signals.

When you added the splitter, it acted as an attenuator. For every 1 dB of attenuation, the IMD is reduced 3 dB. The weaker signals are also attenuated 1 dB, so there is a net gain of 2 dB in the SNR. The splitter made all signals 3.5 dB weaker, the IMD was reduced 10.5 dB, and the net gain in SNR was 7 dB.

Overload can be estimated using the NM numbers or the signal power numbers in dBm.

CBFT has a NM of 75.9 dB, even before adding the antenna gain. If you add a conservative antenna gain of 12 dBd, that brings the NM up to 87.9 dB; clearly overload territory.



Interpreting Noise Margin in the TV Fool Report
Chuck's Digital TV Page

I didn't use CIVM because it is in a different direction.

Using signal power converted to dBmV:
CBFT is -14.9 dBm = +33.9 dBmV
Max input of CM7778 is +34 dBmV; just barely OK
https://www.channelmaster.com/TV_Ant..._p/cm-7778.htm

but if you add the antenna gain:
CBFT 33.9 dBmV + 12 dBd antenna = 45.9 dBmV; preamp overload

using dBm:
CBFT -14.9 dBm + 12 dBd antenna + 16 dB preamp = +13.1 dBm; tuner overload

ATSC Recommended Practice:
Receiver Performance Guidelines


Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

5.1 Sensitivity

A DTV receiver should achieve a bit error rate in the transport stream of no worse than 3x10E-6 (i.e., the FCC Advisory Committee on Advanced Television Service, ACATS, Threshold of Visibility, TOV) for input RF signal levels directly to the tuner from –83 dBm to –5 dBm for both the VHF and UHF bands.

5.2 Multi-Signal Overload

The DTV receiver should accommodate more than one undesired, high-level, NSTC or DTV
signal at its input, received from transmission facilities that are in close proximity to one another. For purposes of this guideline, it should be assumed that multiple signals, each approaching –8 dBm, will exist at the input of the receiver.

THREE TYPES OF OVERLOAD

There are three types of preamp or tuner overload, in order of increasing signal strength:
1. The strong signals almost cause enough intermodulation distortion (IMD) to interfere with the reception of weak desired signals, but the spurious signals are at or below the noise floor of the weak signals. This is the point that holl_ands uses in his preamp charts to obtain max SFDR (Spurious Free Dynamic Range). No damage will happen.

As the strongest signals continue to increase in strength, more of the weaker signals are damaged until you reach:

2. The strong signals cause overload to the preamp or tuner that makes it impossible to receive any signals. No damage will happen. The strongest signals are still there, but they can't be decoded because the IMD products have damaged them so that they contain more errors (high BER....bit error ratio/rate) than can be corrected by the FEC (forward error correction).

3. The signals are so strong that the input transistor is toast. You are not likely to encounter OTA signals that strong, unless you live next door to a high power transmitter and you have your high gain antenna aimed at the transmitter's antenna.

As a general rule, tuners can tolerate stronger signals than preamps before overload. The difference in strength is approx. equal to the preamp gain.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2018-02-02 at 03:41 PM.
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post #14 of 26 (permalink) Old 2018-02-02, 03:38 PM
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As you can see, there is such a thing as too much signal strength.

Your strongest desired signal is CBFT with a signal power of -14.9 dBm. If your weakest desired signal is WFFF with a signal power of -84.1 dBm, the difference is 69.2 dB, which is called your signal dynamic range. To that, you must add the minimum required SNR of 16 dB for your weakest signal to obtain your SFDR (Spurious Free Dynamic Range) of 85.2 dB.



The idea is to adjust the strength of your signals so that their dynamic range matches the possible SFDR of your preamp and tuners, which is what you did when you added the splitter as an attenuator. You added just enough attenuation to reduce the IMD so that your weakest desired signals were not damaged.

Some preamps have a higher SFDR than other preamps; usually the medium gain preamps that are resistant to overload. But, even if your preamp is resistant to overload, you might still overload your tuner.

Here is a preamp comparison chart done by Calaveras. Look for the preamps that can tolerate the strongest input signal and have the highest SFDR:


If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2018-02-02 at 04:05 PM.
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post #15 of 26 (permalink) Old 2018-02-02, 04:20 PM
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Quote:
Getting ABC in my area is not an easy thing to do and I'm fairly sure I'm one of the few in my area (thx to the Tin-Lee filter and the good Old 10Y13S...
I can see how that would be difficult. WVNY is much weaker than your local signals and it has adjacent channel interference from CFCF on real channel 12. I assume that Tin Lee knew about the adjacent channel when they designed your custom filter.

CFCF must not be any stronger than 33 dB more than WVNY to avoid interference. On your report CFCF is 63.2 dB stronger than WVNY, but your filter should help and your antenna pattern should help because they are 24 degrees apart.


If you can not measure it, you can not improve it.
Lord Kelvin, 1883
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