Is this equipment still usable

[gabewinches]

I have just acquired what seems like a vhf/uhf/fm amplifier/distribution system for an apartment building. The antennas on the roof are long gone, but the box is still there. the equipment is very old, as it is probably original to the building. Are these things still usable? if so, how would I hook them up? The "75 ohm uhf/vhf power supply" gives power to a port called "coax from amp" but there was no amplifer, unless its located somewhere else or built into the old antenna

 

[gabewinches]

Sorry if some pictures are duplicated

 

[TheKrell]

Are these things still usable?

Probably; they used to build for the ages. Those pots (tuners for specific channels?) might be dirty and noisy after so long not being moved.

 

[Tower Guy]

The tuners are still useful as FM notch filters. If I remember right, your can have one very deep notch or two modest notches per filter.

The amplifier is good for channels 2-13 only. It is not designed for UHF.

I am not familiar with that power supply.

 

[gabewinches]

So you basically there is 2 fm traps, which i assume help eliminate fm frequencies. then those go into the 4 sets of dials, which i assume you tune those dials to reject a certain fm frequency. If those reject fm how do I tune them? The fm channels I would be trying to block are 89.5, 91.1, 99.9, and 107.9, as there is a radio tower broadcasting those frequencies at the end of my street. The tower also broadcasts a few tv channels, would the tv and amplifier get overloaded because of this station?

 

[rabbit73]

So you basically there is 2 fm traps, which i assume help eliminate fm frequencies. then those go into the 4 sets of dials, which i assume you tune those dials to reject a certain fm frequency.

Thank you for the interesting photos.

If those reject fm how do I tune them? The fm channels I would be trying to block are 89.5, 91.1, 99.9, and 107.9, as there is a radio tower broadcasting those frequencies at the end of my street.

You could tune them with an RTL-SDR.COM V3 dongle ($25-35) and free SDRsharp software from Airspy/com.
Buy RTL-SDR Dongles (RTL2832U)

SDR# and Airspy Downloads - airspy.com

Video
Download and view now. Takes a while to download. I use VLC media player:
2021-01-18 20-02-23 FM with RTL-SDR.mp4

Download and view later:
https://www.dropbox.com/s/pi3l1g64cvv5n6p/2021-01-18 20-02-23 FM with RTL-SDR.mp4?dl=1

The tower also broadcasts a few tv channels, would the tv and amplifier get overloaded because of this station?

Probably, but we would need to see a signal report for your location. You can do one here (I use coordinates from Google maps):
RabbitEars.Info

 

[rabbit73]

This is a generic report for your zip code, but it probably isn't accurate for your actual location:
RabbitEars.Info

 

[gabewinches]

RabbitEars.Info

RabbitEars, where you can learn all about local, over-the-air TV channels.

www.rabbitears.info

There is my signal report, I have an old antennas direct clearstream about 25 feet up outside with no amplifier, getting about 58 channels facing towards nyc.


Sent from my iPhone using Tapatalk

 

[gabewinches]

This is a generic report for your zip code, but it probably isn't accurate for your actual location:
RabbitEars.Info

I think its a report by location. I did the report for my house and did another report right down the hill toward the end of my street and there is significantly less receivable channels, as well as the transmitter located close by, wedw the signal level changes from my house to the end of my street

^my house

end of the street, 1/4 mile away


Sent from my iPhone using Tapatalk

 

[Frank Navin]

It would likely still work, as there is no difference in distribution when it comes to digital vs analog signals.

However the technology is so cheap today, it’s likely not worth Messing with.


Sent from my iPhone using Tapatalk

 

[rabbit73]

I think its a report by location.

Yes, I only had your zip code, so I let the Google maps for the TVFool interactive browser pick the center of the zip code, which was near the Middlebrook School.

I did the report for my house and did another report right down the hill toward the end of my street and there is significantly less receivable channels, as well as the transmitter located close by, wedw the signal level changes from my house to the end of my street

Thank you for the two reports. Reception at the end of the street is worse because your elevation is about 128 ft higher.

WEDW and your FM signals are extremely strong, so your concern about overload is justified. This is an extract of your report in dBm for comparisons:

Note the "R" for WEDW in the last column to indicate reduced coverage for some reason. There are 6 transmitters listed for WEDW:
RabbitEars.Info

When I click on Map in your report for WEDW to show the coverage map, it shows the coverage for 0000077937, which is the STA 200 kW transmitter at Trumbull. For repack, WEDW was supposed to move to a 1000 kW transmitter at 41.052833, -73.563056 in Stamford. If it does, that will solve your overload problem with WEDW, but you will still be left with strong local FM transmitters:
http://www.fmfool.com/modeling/tmp/0ad31740bc/Radar-FM.png

The rabbitears.info report assumes a dipole for an antenna, so you must add the gain of your antenna. When you are close to the transmitter, the actual signal strength might be less than listed because the antenna signal lobe in the vertical plane is narrow and above your location. The software doesn't take that into consideration. You would need a signal level meter to measure the actual strength of the signal.

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 (-34 dBmV) to –5 dBm (+44 dBmV)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 (+41 dBmV), will exist at the input of the receiver.

Presumably for Two Strong Input Signals.
Max Signal Input and Output would need to be DERATED for more than two strong signals.

You will need to find a way to attenuate the WEDW signal with some kind of trap. A custom CH21 trap can be made by Tin Lee in Canada (expensive), or by Jan Jenca on Ebay (less expensive). It is also possible to fabricate a trap with coax as described by Tower Guy in another thread.

 

[gabewinches]

WEDW is staying. They are channel sharing with others, including WZME, which is moving to another place. CT Public Television just got approval to remove their side mounted antenna, put a new antenna at the top. and upgrade their transmitter. Since the increased height of the antenna, and beam tilt of 1.2 degrees, I will probably be under the majority of the signal. I am only 900 feet from the tower.



There is the construction plan, which shows WEDW is staying

https://portal.ct.gov/-/media/CSC/2_EMS-medialibrary/Trumbull/BoothHillRd_VideoLa/CTPublicBroadcasting/EM-CPB-144-201120_filing_-800-BOOTH-HILL-RD-TRUMBULL-873128.pdf

 

[rabbit73]

WEDW is staying. They are channel sharing with others, including WZME, which is moving to another place. CT Public Television just got approval to remove their side mounted antenna, put a new antenna at the top. and upgrade their transmitter. Since the increased height of the antenna, and beam tilt of 1.2 degrees, I will probably be under the majority of the signal. I am only 900 feet from the tower.

There is the construction plan, which shows WEDW is staying

https://portal.ct.gov/-/media/CSC/2_EMS-medialibrary/Trumbull/BoothHillRd_VideoLa/CTPublicBroadcasting/EM-CPB-144-201120_filing_-800-BOOTH-HILL-RD-TRUMBULL-873128.pdf

Thank you for the link. It looks like you will be stuck with the blowtorch.

I see another tower NNW of the WEDW tower; what is that for?

 

[gabewinches]

Thank you for the link. It looks like you will be stuck with the blowtorch.

I see another tower NNW of the WEDW tower; what is that for?

View attachment 149935

View attachment 149936

View attachment 149937

The small tower is an old at&t long lines site, not used anymore now with cellular, 2-way radio and a couple of microwaves dishes

https://www.long-lines.net/places-routes/maps/MW6610-E-inset4.jpg

 

[rabbit73]

A Channel Plus NF-470 Notch Filter will take out RF 21.
NF-470: Notch Filter
Removes CATV channels 70-74 and UHF channels 19-23
Freq: 499.25MHz - 523.25MHz

 

[gabewinches]

A Channel Plus NF-470 Notch Filter will take out RF 21.
NF-470: Notch Filter
Removes CATV channels 70-74 and UHF channels 19-23
Freq: 499.25MHz - 523.25MHz

Thanks for the recommendation. That would be something good as the channel would be operating at 515 mhz, or channel 21. Are there any filters that would just block 21, or is that really my only option. Worst case scenario I lose a couple stations between 19-23

 

[rabbit73]

Thanks for the recommendation. That would be something good as the channel would be operating at 515 mhz, or channel 21. Are there any filters that would just block 21, or is that really my only option. Worst case scenario I lose a couple stations between 19-23

I don't have a curve for the NF-470, but this is the curve for the lower channels NF-469. At least it gives you the shape of the curve at the ends:

There are single channel attenuation filters, but they would be custom made. I was looking for something ready-made.

A single channel CR7 Bandstop filter for channel 21 from Tin Lee would probably be over $100
Tin Lee Electronics :: MATV Bandstops

A single channel bandstop filter from Jan Jenca would probably be less than $50. He is in Slovakia and sells on Ebay. A lot of the guys on the AVS Forum have ordered from him. For example:

Jan Jenca antenna components

Items for sale by jan_jenca | eBay

UHF one channel-stop filter, UHF FIX one channel stop filter | eBay

His difference between notch and bandstop isn't completely clear to me for your application. Ask him.

 

[Tower Guy]

I would also suggest the NF- 470 filter. The rejection of WEDW would be 30db more than the Jan Jenca filter. I don’t see any useful stations that could be received using any other affordable bandstop filter.

I would continue using the tunable FM traps as-is. Tuning them could be confusing. When I played with those traps many years ago I used the signal strength meter on my component FM receiver to tune for minimum signal.

 

[rabbit73]

If you use a filter, it is important that the coax be grounded to the house electrical system ground. Otherwise, the CH21 signal might bypass the filter and get directly into the TV tuner.

I don't have a curve for the notch filter, but it looks like the bandstop filter takes a bigger chunk out of the spectrum but gives more attenuation at the design frequency. Maybe the notch filter would be better for you even though it gives less attenuation at the design frequency, but I'm not sure.

Show your signal report in your Jan Jenca email when you ask questions. The filter will wipe out CBS on 22 but you have CBS on 36.

 

[gabewinches]

I bought the USB dongle for analyzing frequencies. So there are 4 sets of FM traps. 2 of the sets say hi "q" trap hi band. what frequency is this referring to? and the other 2 say hi "q" trap lo band/fm, Obviously these 2 are blocking fm, but what are they referring to when they say lo band?

This is my plan on how I am going to have everything wired up
antenna>grounding block>nf 470 filter>2 channel master FM traps model 7204>4 channel master (2)7008 (2)7009> amplifier(recommendations would be nice)>tv

also If you look at the gray box in the pictures at the top of the thread, that says ch 24 to 11. single-channel converter. It has a uhf input and vhf output. Is this a converter when uhf tv was new and TVs didn't have a UHF tuner ?
in the second VHF port it seems to have a channel filter, guessing by the model number it is for rf channels 1-12