I know that the attenuation will be less at VHF than UHF/700/800, but for somebody trying to improve reception, starting with a compromised setup isn't going to be necessarily helpful. That's all.
Seeking Feedback on Rail Band Reception Improvement Options
- Thread starter MDScanFan
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I know that the attenuation will be less at VHF than UHF/700/800, but for somebody trying to improve reception, starting with a compromised setup isn't going to be necessarily helpful. That's all.
Does anybody here have experience with Mini-Circuits passband filters for railroad VHF voice? I see they are exponentially cheaper than the preselectors from STI-CO, Polyphaser and/or Sinclair. The model in particular I was trying to link was SXBP-162+, which is said to be a "Lumped LC Band Pass Filter, 155-169 mHz."
Lumped LC Band Pass Filter, 155 - 169 MHz, 50Ω | SXBP-162+ | Mini-Circuits
Mini-Circuits is a global leader in the design and manufacturing of RF, IF, and microwave components from DC to 86GHz.
www.minicircuits.com
Does anybody here have experience with Mini-Circuits passband filters for railroad VHF voice? I see they are exponentially cheaper than the preselectors from STI-CO, Polyphaser and/or Sinclair. The model in particular I was trying to link was SXBP-162+, which is said to be a "Lumped LC Band Pass Filter, 155-169 mHz."
Lumped LC Band Pass Filter, 155 - 169 MHz, 50Ω | SXBP-162+ | Mini-Circuits
Mini-Circuits is a global leader in the design and manufacturing of RF, IF, and microwave components from DC to 86GHz.www.minicircuits.com
I don't but I have one of these and it seems to work well,
AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz in Enclosure | eBay
This is a 3rd orderAIS bandpass filter in an enclosure, with excellent sideband rejection. This product is ideally suited for AIS receiver applications at 162 MHz . AIS uses the high side of the duplex from two VHF radio "channels" (87B) and (88B).
www.ebay.com
He also sells one without a case for a little cheaper,
AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz | eBay
This is a 3rd orderAIS bandpass filter with excellent sideband rejection. This product is ideally suited for AIS receiver applications at 162 MHz . AIS uses the high side of the duplex from two VHF radio "channels" (87B) and (88B).
www.ebay.com
If you try the Minicircuts model let us know how it works. They both have some insertion loss even with the passed frequencies.
That one doesn't appear to be tight enough to block out NOAA weather radio or VHF paging transmitters.
If there is one that can let the railroad frequencies through but block NOAA I would sure love to know about it!
I was considering those based on the low price. The insertion loss is a bit high at 3 dB. Depending on the scenario (ex strong rail signals but you have FM overload issues) that much IL may be fine.
I don't but I have one of these and it seems to work well,
AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz in Enclosure | eBay
This is a 3rd orderAIS bandpass filter in an enclosure, with excellent sideband rejection. This product is ideally suited for AIS receiver applications at 162 MHz . AIS uses the high side of the duplex from two VHF radio "channels" (87B) and (88B).www.ebay.com
He also sells one without a case for a little cheaper,
AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz | eBay
This is a 3rd orderAIS bandpass filter with excellent sideband rejection. This product is ideally suited for AIS receiver applications at 162 MHz . AIS uses the high side of the duplex from two VHF radio "channels" (87B) and (88B).www.ebay.com
If you try the Minicircuts model let us know how it works. They both have some insertion loss even with the passed frequencies.
Yeah the insertion loss is a down side, however I'm using mine after my preamp so it isn't as big of a deal for me and it works for my setup. It would be interesting to compare results with it before and after a preamp.
The Mini Circuits unit also has insertion loss although not quite as much.
Do you know what kind of connectors the Mini Circuits unit has?
The Mini Circuits unit also has insertion loss although not quite as much.
Do you know what kind of connectors the Mini Circuits unit has?
How much loss can you handle? The NOAA frequencies are so close to the rail band that it would be hard to notch them out without incurring a lot of pass band loss. Par offers a 162 notch filter that gives around 3-7 dB (eyeballing it) loss in the rail band.
prcguy
Member
Using an actual railroad transceiver like a Clean Cab Spectra or high end commercial radio should not require any filtering to keep out NOAA weather or anything else, just hook it up and enjoy beautiful reception.
I agree, it is VERY rare that I ever have any kind of intermod with my Motorola CDM1550, I think I had NOAA bleed in once when I was literally right next to the tower and it only lasted for a few seconds.
how far are you looking to pick up
I am trying to listen within a ~8-10 mile radius. I believe I get much of the traffic within that radius. I am mainly trying to improve signal quality at this point.
I can positively state that on my Yaesu FT-8900R with the Sti-Co preselector and a simple LNA preamp with a 5/8th wave whip, I've never experienced NOAA bleed. And I can say that while being within 50 yards, dead level elevation, line of sight of KZZ41's antenna on Mount Washington on the Yankee Building.
As to IL, you're going to have insertion loss with anything you use. The quality of the product will obviously determine how much. Those cheap MiniCircuit ones have an average 3dB loss, while the professional Sti-Co and PolyPhaser preselectors have an IL of 1.5dB or less.
RR build there base stations for about 20miles coverage. maybe try beam
The base stations come booming in. The portable radios are the ones that come in weak. I am trying to improve those. I received my collinear antenna but the weather has not been cooperating. I will report back once I get to play with it.
You'll unfortunately have that when those HTs barely get two mile range. It's getting to the point trains are so long if a conductor is working a cut at the end of a long train their handheld won't reach the engine unless they step away from the train and stick their radio in the air.
It is possible to pick up the hand held radios farther away but you need the right conditions. My antenna is exactly 5.2 miles from the yard here in Jefferson City, I can usually always pick up switching operations, both the locomotive and the hand held. At times I can even pick up the conductor on Amtrak calling out car distances to tell the engineer where to stop and he is inside the coach. I have a big antenna at a great receive site so that is a big help.
An update...I have the Laird omni mounted on a tree in my yard at around 15’ at its base. Definitely an improvement over my discone in the attic. By switching among the antennas I can tell the signals on the Laird are much stronger and clearer even with my subpar cable run. The cable run needed to get to the antenna is about 150’. I rolled up the loss to be about 5 dB, which I realize is a lot.
This evening I installed a HPN-30118 and ZX60-P103LN at the antenna. The preamp has a gain around 24 dB at 160 GHz. At the radio I have a 10 dB attenuator and a 0-10 dB variable attenuator. With the variable atten at around 9 dB the gain of the preamp should roughly counter the cable loss.
I tuned into an extremely weak NOAA broadcast and played with the attenuation. I adjusted it until the signal peaked on intelligibility. It was not an exact science but it seemed like it peaks at total attenuation 15-16 dB so I set it there. Dialing back the attenuation further did not appear to help the desired signal quality. At this hour there are not too many rail signals for me to monitor so I can’t really assess how well it works.
Am I thinking about attenuation settings the right way? Is there a better approach to take when dialing in the attenuation?
This evening I installed a HPN-30118 and ZX60-P103LN at the antenna. The preamp has a gain around 24 dB at 160 GHz. At the radio I have a 10 dB attenuator and a 0-10 dB variable attenuator. With the variable atten at around 9 dB the gain of the preamp should roughly counter the cable loss.
I tuned into an extremely weak NOAA broadcast and played with the attenuation. I adjusted it until the signal peaked on intelligibility. It was not an exact science but it seemed like it peaks at total attenuation 15-16 dB so I set it there. Dialing back the attenuation further did not appear to help the desired signal quality. At this hour there are not too many rail signals for me to monitor so I can’t really assess how well it works.
Am I thinking about attenuation settings the right way? Is there a better approach to take when dialing in the attenuation?
prcguy
Member
You should really get a band pass filter for the RR band to put in front of the preamp. 24dB gain is way too much and some attenuation will be needed but it could be the preamp is getting overloaded by strong FM or TV broadcast, paging, etc, and creating lots of Intermod which can masquerade as a high noise floor. Once you get a band pass filter you can use the variable attentuator to find the best attenuation to use then replace that with a cheap fixed attenuator.
I find about 10dB is the most gain you want to add to the system before some receivers will start to complain. You can usually get away with 2 to 4dB extra system gain without problem and that's all you would ever need unless your running an old numb tube type receiver.
I find about 10dB is the most gain you want to add to the system before some receivers will start to complain. You can usually get away with 2 to 4dB extra system gain without problem and that's all you would ever need unless your running an old numb tube type receiver.
I will keep an eye out for some bandpass filtering but for now I am working with what I have on hand to get a feel for the situation. Interestingly, some of the filters recommended to me, such as the Sti-co and polyphaser, seem to provide no rejection at the pager bands.
The filter in front of the preamp provides decent FM band rejection and well as rejection of the AM BCB. Thus far I have seen no indication of overload. I think it will more interesting during the day when I have more signals (wanted and unwanted) to contend with.
One observation during the (not amplified) collinear to discone testing was that on some channels the discone would produce a higher s-meter level but this really meant a higher noise level and lower signal level. I assumed this was attributed to the broadband discone picking up more noise than the narrow band collinear.
The filter in front of the preamp provides decent FM band rejection and well as rejection of the AM BCB. Thus far I have seen no indication of overload. I think it will more interesting during the day when I have more signals (wanted and unwanted) to contend with.
One observation during the (not amplified) collinear to discone testing was that on some channels the discone would produce a higher s-meter level but this really meant a higher noise level and lower signal level. I assumed this was attributed to the broadband discone picking up more noise than the narrow band collinear.
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