Bandpass for P25

[Merovingian]

Here is a great filter for the 935-941MHz range and these have super tight skirts. CELWAVE FILTER 5098-5-10 rack mount 935-941 MHZ BRAND NEW SEALED IN BUBBLE WRAP | eBay

Similar units show up for the 851 to 860 something band for good prices.

Wow!! Those are hefty units! I put in an order for two of them, they look better than anything I've see so far and the price is good, plus they are new. I was wanting to mount them at the antenna but I guess these will have to be inside, on the floor, mount filters.

How did you find these? I searched and searched and nothing came up except stuff from Israel or cell phone filters that "block" the frequencies I wanted. . .

Thanks again. You are a genius.

 

[Merovingian]

Aah, this one might do for your 850-860 range. Celwave 0182452V05 851-866MHz Filter | eBay

I ordered this one too. I wanted two but even one that does what I want will work fine. I may have to get an amplified splitter to use with two or four SDR radios or something though.

Thanks once again!

 

[prcguy]

I buy a lot of this kind of stuff for repeater master receive front ends, etc, and know what to look for. I've bough similar units for UHF and 900MHz but had to retune them slightly.

Wow!! Those are hefty units! I put in an order for two of them, they look better than anything I've see so far and the price is good, plus they are new. I was wanting to mount them at the antenna but I guess these will have to be inside, on the floor, mount filters.

How did you find these? I searched and searched and nothing came up except stuff from Israel or cell phone filters that "block" the frequencies I wanted. . .

Thanks again. You are a genius.

 

[Merovingian]

I buy a lot of this kind of stuff for repeater master receive front ends, etc, and know what to look for. I've bough similar units for UHF and 900MHz but had to retune them slightly.

I see. While you are on a roll. . . Any ideas for a high quality amplified splitter 1X4 or so with and "N" connector on the input side I could use with the 800MHz and 900MHz filters?

 

[prcguy]

There are all kinds of surplus splitters from Celwave that cover that frequency range and some go for $5 at swap meets. Here is one on Ebay but I've only seen them with BNC connectors. These are typically used in receiver distribution systems for trunking radio and cell phone base stations.

Celwave Splitter PD7727 Frequency 800-960 UHF Radio Module 7445235010081 | eBay

Find many great new & used options and get the best deals for Celwave Splitter PD7727 Frequency 800-960 UHF Radio Module at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Otherwise MiniCircuits should make something similar and possibly with N connectors.

I see. While you are on a roll. . . Any ideas for a high quality amplified splitter 1X4 or so with and "N" connector on the input side I could use with the 800MHz and 900MHz filters?

 

[prcguy]

Aah, here ya go, and the price is right. Mini-circuits ZB4PD1-930W PWR DIV / N 725-1050MHz | eBay

Or this one looks just as good for your purposes. Mini-circuits ZB4PD1 PWR DIV / N 800-2000MHz 797822770227 | eBay

 

[Merovingian]

Aah, here ya go, and the price is right. Mini-circuits ZB4PD1-930W PWR DIV / N 725-1050MHz | eBay

Or this one looks just as good for your purposes. Mini-circuits ZB4PD1 PWR DIV / N 800-2000MHz 797822770227 | eBay

Great! Thank you for your help!

You are a king among men

 

[prcguy]

Thanks, but I'm really just some guy among a big pile of radio crap.

Great! Thank you for your help!

You are a king among men

 

[Merovingian]

Thanks, but I'm really just some guy among a big pile of radio crap.

Hahahaha All of your information is almost always spot on. You should look into starting a YouTube channels or something and become a social media influencer for radio communications. I've probably bought more radio stuff that you have recommended or pointed me toward than anything else.

 

[cmdrwill]

Thanks, but I'm really just some guy among a big pile of radio crap.

I did not know that! But prcguy really does know his stuff....

 

[a417]

Does anyone know of a good bandpass filter for the 850-860 MHz frequency range and maybe for the 935-940 MHz range. I've spent the last few

What frequencies are you looking to restrict? Maybe a low-pass or a high-pass can help, instead of a band-pass - if you can't find what you ideally want?

 

[Merovingian]

What frequencies are you looking to restrict? Maybe a low-pass or a high-pass can help, instead of a band-pass - if you can't find what you ideally want?

Anything but 850-860 MHz, 935-940 MHz. iMonitor and prcguy pointed me to what I was looking for.

 

[prcguy]

I would still mount them at the antenna(s) and you can place a low noise preamp right after each filter then combine them. The 3dB or so loss from combining will not matter since it would be after a preamp.

Here is a great little preamp for that frequency range with about .55dB noise figure, 18dB gain, 1dB compression point of 16dBm and an IP3 of 30dBm. All good specs for $60 brand new. I'm using one right now on a 900MHz repeater front end. Mini-Circuits

 

[Merovingian]

I would still mount them at the antenna(s) and you can place a low noise preamp right after each filter then combine them. The 3dB or so loss from combining will not matter since it would be after a preamp.

Here is a great little preamp for that frequency range with about .55dB noise figure, 18dB gain, 1dB compression point of 16dBm and an IP3 of 30dBm. All good specs for $60 brand new. I'm using one right now on a 900MHz repeater front end. Mini-Circuits

Ahhh, I see. Thanks for the link, it looks good and the price isn't bad.

Yet another question, about powering the preamp, not just this one but I was planing to use preamps on at least three other antennas I was wanting to put up in the future.

I was looking at Bias Tee's and to buy three sets, and now a fourth set, one for inside and one for outside at the antenna, it is getting pretty expensive. I wanted to get your opinion on my choice that I had been planing to use for all of my preamps.

I had previously chosen this one for inside, to inject power into the coax cable. I liked the BNC connector because it is secure and easy to connect:
Mini-Circuits $82.95 for one seems a bit high.

This is the one I has chosen for outside at the antenna to power the preamp:
https://www.minicircuits.com/WebStore/dashboard.html?model=ZFBT-282-1.5A+ $59.95 is a little better but when buying four of these the price gets steep .

The preamps seem to run off of 5V so the Bias Tee's shouldn't "need" to be that expensive should they? Right now, with my current choices, I'm looking to spend about $572 just to power four preamps for four different antennas. That doesn't include the cost of the preamps them selves, the attenuators nor the common mode choke I may put at either end of the coax for certain antennas.

Then I need an enclosure at the antenna to protect the components. To house the choke and other components and to have room to work I was looking at the outdoor version: WH-22 $62.82

A mounting panel: WH-22K $17.10

A pole mount kit: PK-127 $53.11

Needless to say, at the moment with my current thinking and choices I'm looking to spend many hundreds of dollars for each antenna to support a preamp for each antenna. . .

I've been hesitating to add preamps to anything because of the associated cost of all of the the other components that go along with a preamp. Maybe you have some different ideas or could straighten out my thinking?

Thanks again

 

[prcguy]

You don't have to buy a Minicircuits Bias Tee but there are some cheap ones now and then on Ebay like this: MINI-CIRCUITS ZFBT-4R2G+ BIAS TEE 10-4200 MHz | eBay

For some of my recent projects I bought Chinese Bias Tees and they work just fine, especially for the price. RF Translator Broadband Radio Frequency Microwave 10MHz-6GHz Bias Tee with Case | eBay

I bought several and they did the job until I changed out the preamp for a power hog and then added two transfer relays bringing the DC current up to 1.5 amps. So I got these and they are working fine at that current. You can possibly run all your preamps off one Bias Tee with one of these: Coaxial Bias Tee 10MHz-6GHz 2A 50V Broadband Radio Frequency Microwave Coaxial | eBay

If the total current for all your preamps is under 2A and they are all in the same box, then use just one Bias Tee in the house and one at the preamps then wire the DC from that Bias Tee to all amps, saves a lot of money

The enclosure you listed is for indoor use. I bought one of these or a similar model for my outdoor filter/preamp project. It wont fit all your filters but the brand seems ok for the price. ALTELIX NP17146 Policarbonate ABS NEMA Box Outdoor Enclosure Gray | eBay

 

[devicelab]

I get my filters from EBAY... search for K&L MICROWAVE... they make tubular filters usually with SMA-M or SMA-F connectors. There's a guy in Israel that sells a lot of used filters and he ships fast.

Also be sure to learn how to read bandpass filters... e.g. for my 900 Mhz filter it's labeled 5B120-900/T200 ...so 5B120 is the type and 900 is the center frequency... and the last number is the bandwidth... so 800-1000 Mhz.

I don't think I've ever paid more than $50 for a used filter. I've been lucky as mine are all high quality.

FWIW, my 800 Mhz filter is also tubular and super thin... size of a pencil with SMA-F ends. It's made by an Israeli company "AEL" which gets me 698 to 875 Mhz... perfect for 700/800 bands...

Cheers!

PS. You're in luck... he has multiple AEL filters for sale.

RF Microwave BPF Band Pass Filter 685-860 MHz SMA Tested | eBay

SMA Connectors (f/f). Microwave Band Pass Filter. Frequency range: 685-860 MHz. We can't declare a lower value than the real item value unless it was discussed and. Tested, see pictures! best solution for you if possible.

www.ebay.com

Check out his store... the filters are under "MIcrowave Filters"

 

[Merovingian]

You don't have to buy a Minicircuits Bias Tee but there are some cheap ones now and then on Ebay like this: MINI-CIRCUITS ZFBT-4R2G+ BIAS TEE 10-4200 MHz | eBay

For some of my recent projects I bought Chinese Bias Tees and they work just fine, especially for the price. RF Translator Broadband Radio Frequency Microwave 10MHz-6GHz Bias Tee with Case | eBay

I bought several and they did the job until I changed out the preamp for a power hog and then added two transfer relays bringing the DC current up to 1.5 amps. So I got these and they are working fine at that current. You can possibly run all your preamps off one Bias Tee with one of these: Coaxial Bias Tee 10MHz-6GHz 2A 50V Broadband Radio Frequency Microwave Coaxial | eBay

If the total current for all your preamps is under 2A and they are all in the same box, then use just one Bias Tee in the house and one at the preamps then wire the DC from that Bias Tee to all amps, saves a lot of money

The enclosure you listed is for indoor use. I bought one of these or a similar model for my outdoor filter/preamp project. It wont fit all your filters but the brand seems ok for the price. ALTELIX NP17146 Policarbonate ABS NEMA Box Outdoor Enclosure Gray | eBay

Thank you again for the links! You sure have a lot of information. This gives me a few more choices now, I'm glad these are cheaper. I will put these into my equipment spreadsheet.

Yeah the enclosure I listed defaults to the "indoor" version when the page loads, you have to click the "outdoor" button to get the outdoor version. The way I'm planning to setup my equipment I'm going to use one box per antenna and one bias tee set per antenna rather than one cable running to one box with many different components in it for many antennas. Right now I'm connecting and disconnecting three different antennas with three different cables from my SDR and sometimes using different SDRs, depending on what I want to listen to.

 

[Merovingian]

I get my filters from EBAY... search for K&L MICROWAVE... they make tubular filters usually with SMA-M or SMA-F connectors. There's a guy in Israel that sells a lot of used filters and he ships fast.

Also be sure to learn how to read bandpass filters... e.g. for my 900 Mhz filter it's labeled 5B120-900/T200 ...so 5B120 is the type and 900 is the center frequency... and the last number is the bandwidth... so 800-1000 Mhz.

I don't think I've ever paid more than $50 for a used filter. I've been lucky as mine are all high quality.

FWIW, my 800 Mhz filter is also tubular and super thin... size of a pencil with SMA-F ends. It's made by an Israeli company "AEL" which gets me 698 to 875 Mhz... perfect for 700/800 bands...

Cheers!

PS. You're in luck... he has multiple AEL filters for sale.

RF Microwave BPF Band Pass Filter 685-860 MHz SMA Tested | eBay

SMA Connectors (f/f). Microwave Band Pass Filter. Frequency range: 685-860 MHz. We can't declare a lower value than the real item value unless it was discussed and. Tested, see pictures! best solution for you if possible.

www.ebay.com

Check out his store... the filters are under "MIcrowave Filters"

That is an unusual looking filter. Very compact. I will add this to my equipment spreadsheet. Thanks.

 

[prcguy]

If you need any preamps in the 850 to 940MHz range here is an excellent one that covers 600 to 1100MHz with about .6dB noise figure, 19dB gain, IP1 of 19dBm and IP3 of 35dBm for about $30 surplus. I bought several from the same seller and these were quite expense new. Its better than the one I recommended a few posts up and a lot cheaper.

They are rated for 18 to 36 volts and you pop the cover and bypass a diode and they work in the 12 to 15 volt range just fine.

600-1100MHz LNA 0.6dB NF mini Circuits ZQLSC-1100 | eBay

That is an unusual looking filter. Very compact. I will add this to my equipment spreadsheet. Thanks.

 

[Merovingian]

If you need any preamps in the 850 to 940MHz range here is an excellent one that covers 600 to 1100MHz with about .6dB noise figure, 19dB gain, IP1 of 19dBm and IP3 of 35dBm for about $30 surplus. I bought several from the same seller and these were quite expense new. Its better than the one I recommended a few posts up and a lot cheaper.

They are rated for 18 to 36 volts and you pop the cover and bypass a diode and they work in the 12 to 15 volt range just fine.

600-1100MHz LNA 0.6dB NF mini Circuits ZQLSC-1100 | eBay

Hey! Thats great, thanks for spotting that for me. I appreciate it. You are like the Sherlock Holmes of eBay.

I had ordered three L-Com HGV-906U 800/900 MHz antennas a few days ago, they arrived today. One for use with the 800 MHz filter and two for the two 900 MHz filters I ordered. I'm still waiting for the 800 MHz filter to ship, it is coming from Texas so I don't know what situation the person selling it is in with all of the winter weather that went on. The order page says delivery estimate is today or tomorrow but I never received a notice that it even shipped. Hopefully it did. . .

I also ordered a Uniden SDS100 scanner to try out with the antennas, it also arrived today. After doing a lot of research, it seems the trunk tracking software that is out there for SDRs is "spotty" and still very early in development, assuming it is actually still being developed. I was hoping I could have found a nice polished trunk tracking/decoding software.