Fringe VHF Marine Reception Help Needed

MDScanFan

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I am looking for guidance to help fringe reception of vhf marine transmissions. The distance I am trying to span is around 18-20 miles and I believe there is a slight hill breaking the line of sight along the way. I am limited to attic mounted antennas (wood, shingles, no metal). I am using runs of commscope rg6 that spans 70-100 feet depending on location in the attic. Loss is around 2-2.25 dB per the data sheet. I am working with a few radios: RS Pro 2032, Pro 95, PSR 800. With my attic mounted tram discone antenna I cannot receive any maritime signals.

As a test case I built a 5 element yagi that spans 150-165 MHz. It was designed for 75 Ohm to match the rg6 and at 157 MHz it is modeled at 9.5 dBi realized gain. The cable run is around 100 ft. I have no way to verify the gain but it’s measured vswr at the antenna input matches up nicely with the model. Testing the front to back ratio against NWS transmitters seems reasonable.

I mounted the yagi and pointed it in the desired direction. I now receive some signals including a coast guard station, a commercial land-based maritime transmitter, and very limited ship transmissions. For the signals I do receive I can tell what they are saying but the signals are generally weak and noisy. I am not expecting too much based on my location and installation limitations but I would like to see if I can clean up the signals I do receive and possibly get some more.

I am considering my options to try to improve reception. Ideas:

  • Increase gain of yagi by 2-3 dB
  • Add preamp and possibly FM trap at antenna. I’ve never worked with these before.
  • Lower loss coax - Running new coax is a pain so I would like to avoid it if possible. Also, I cannot easily run larger than ~0.25” diameter given the routing needed.
  • Anything else?

I am seeking advice for my situation and for prioritizing what to try next. Thank you.
 

Arkmood

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Taney County MO
I am looking for guidance to help fringe reception of vhf marine transmissions. Thank you.
Was in same situation - attic,east coast,vhf marine target freqs.
My solution:
Add rotor to yagi.
Install legit marine base antenna, even if you have to tilt to fit, or base loaded marine ant. (used Shakespeares at my setup) switched between two.
Use low noise preamp - to overcome 100ft. cable loss.
Better coax always a plus...
 

MDScanFan

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USA
Thank you for the reply. I considered a more traditional marine base antenna, such as a collinear, but I do not think I could get the gain I need.
The max height of my attic is around 8-9’ and that probably means a marine vertical with around 6 dBi of gain. The yagi gets 9 dBi in the desired direction.

Also a rotor will not help in this situation because I only care about one direction and I don’t have the turn radius for rotation anyway.

Given my installation limitations I think a yagi is my best bet. I believe it boils down to higher gain yagi, preamp, and/or better coax. Not sure which one is worth tackling first.
 

JoshuaHufford

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I think you went the right direction with a yagi, I've had good success with weak signals using them over an omni antenna.

Can you bring your radio up in the attic and run a short coax jumper from the antenna to it to see if reducing coax loss will improve things? I know it is probably hot up there but that should help answer that question.

What kind of radio/scanner are you using? My main interest in scanning is the railband which is all around 160-162Mhz, and I've noticed an improvement in performance using older Motorola commercial radios as opposed to a scanner.

I know this subject is debated a lot here, but if you do end up running new coax you might as well keep the impedance the same across the entire system, might help you gain a little bit of signal there. I imagine your radio is probably looking for 50 ohms? You should be able to run LMR-240 and keep it under your size restriction, but LMR-240 doesn't have much better loss than RG-6. I'm sure others with more experience can offer better input in this area but if you truly are restricted to .25" for your coax replacing it might not be worthwhile.

BTW for loss I'm seeing at 160MHz 3.8db for RG-6 and 3.5db for LMR-240 per 100ft. You are loosing over half of your signal in your coax.

A preamp certainly may help in your situation, but if you have any strong signals nearby it might make things worse. If you get a preamp buy a quality unit with low noise, don't go cheap. Might plan on getting a variable attenuator or a couple different value attenuators as well as you can often end up with too much signal at your radio which can make things worse. In my experience commercial radios are also much better at dealing with strong signals when using a preamp than a scanner is.
 

Ubbe

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I use a Diamond F23 VHF antenna that comes with a cutting diagram to make it work at higher frequencies than the 145Mhz it's factory tuned to. It works excellent for marine VHF but its size are too big for attic use.

An amplifier and FM filter would be a good option. Try a PGA103+ based amplifier that costs $25 that have low noise that will increase the total sensitivity of your scanner and feed it thru the coax and install up at the antenna. That will give you at least a 3dB increase in signal, double up.
But you have to attenuate the signal at the scanner to a usable level. Maybe a 10dB attenuation will be enough.

I buy the circuit board types
Ultra Linear LNA 0.01-2 GHz Gain>20dB PGA-103 ESD Protection+ Gain Stabilization | eBay
but Mini-Circuit have it in a metal box if you prefere that, at a doubled cost.
https://www.minicircuits.com/WebStore/dashboard.html?model=ZX60-P103LN%2B

If it's only the marine band you want to receive then it might be a bandpass filters that can be used that will eliminate any other filters. This one goes from 150-165Mhz that's maybe ideal for marine monitoring. Put that between amplifier and scanner to compensate for the 3dB loss in it.
AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz | eBay

/Ubbe
 

MDScanFan

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Bringing the radio up the the attic is a great suggestion. I will try that when I get a chance. As you point out, it should help answer the coax question.

I just checked and my coax is Commscope F677TSVV. The data sheet shows 2 dB / 100’ at 85 MHz and 2.9 dB at 187 MHz. So probably 2.7 dB loss for my run at 156 MHz. For reference, and equivalent LMR 400 run is around 1.8 dB, which is about 20% less loss. Not a huge difference.

Regarding the radio, I am running tests on a couple few older RS analog scanners and a PSR 800. I do see more reception variation among them than I was expecting. I will take a closer look at the specs to see if I can tie them to the differences I hear. Perhaps there is something to be gained with a radio with better marine band sensitivity. I plan to dedicate the antenna and a radio to marine band reception so I would be fine with getting a radio that is optimized for marine band only.


I think you went the right direction with a yagi, I've had good success with weak signals using them over an omni antenna.

Can you bring your radio up in the attic and run a short coax jumper from the antenna to it to see if reducing coax loss will improve things? I know it is probably hot up there but that should help answer that question.

What kind of radio/scanner are you using? My main interest in scanning is the railband which is all around 160-162Mhz, and I've noticed an improvement in performance using older Motorola commercial radios as opposed to a scanner.

I know this subject is debated a lot here, but if you do end up running new coax you might as well keep the impedance the same across the entire system, might help you gain a little bit of signal there. I imagine your radio is probably looking for 50 ohms? You should be able to run LMR-240 and keep it under your size restriction, but LMR-240 doesn't have much better loss than RG-6. I'm sure others with more experience can offer better input in this area but if you truly are restricted to .25" for your coax replacing it might not be worthwhile.

BTW for loss I'm seeing at 160MHz 3.8db for RG-6 and 3.5db for LMR-240 per 100ft. You are loosing over half of your signal in your coax.

A preamp certainly may help in your situation, but if you have any strong signals nearby it might make things worse. If you get a preamp buy a quality unit with low noise, don't go cheap. Might plan on getting a variable attenuator or a couple different value attenuators as well as you can often end up with too much signal at your radio which can make things worse. In my experience commercial radios are also much better at dealing with strong signals when using a preamp than a scanner is.
 

MDScanFan

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I will order a preamp and some filtering to see if that helps. I have some flamethrower FM stations (~-45 dBm at radio input) in my area so I think an fm filter before the preamp is needed. I plan to go with the HPN-30118. The AIS filter you found looks interesting and I will keep it mind. If I go with an fm filter before the preamp, then I do not the AIS filter after the preamp would provide much benefit in my situation. But it is inexpensive so I may it get it as well.

I was leaning towards the mini circuits ZX60-P105LN because the gain is not too high at 14 dB, low NF, and decent 1dB compression. I will take a look at the PGA103+ before I place the preamp order. Either way, as you point out, I need to get an attenuator in the path. Thank you for your reply.


I use a Diamond F23 VHF antenna that comes with a cutting diagram to make it work at higher frequencies than the 145Mhz it's factory tuned to. It works excellent for marine VHF but its size are too big for attic use.

An amplifier and FM filter would be a good option. Try a PGA103+ based amplifier that costs $25 that have low noise that will increase the total sensitivity of your scanner and feed it thru the coax and install up at the antenna. That will give you at least a 3dB increase in signal, double up.
But you have to attenuate the signal at the scanner to a usable level. Maybe a 10dB attenuation will be enough.

I buy the circuit board types
Ultra Linear LNA 0.01-2 GHz Gain>20dB PGA-103 ESD Protection+ Gain Stabilization | eBay
but Mini-Circuit have it in a metal box if you prefere that, at a doubled cost.
https://www.minicircuits.com/WebStore/dashboard.html?model=ZX60-P103LN%2B

If it's only the marine band you want to receive then it might be a bandpass filters that can be used that will eliminate any other filters. This one goes from 150-165Mhz that's maybe ideal for marine monitoring. Put that between amplifier and scanner to compensate for the 3dB loss in it.
AIS 162 MHz Band Pass Filter Bandpass 160 MHz 161 MHz 162 MHz | eBay

/Ubbe
 

Groeteschele

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Apr 6, 2020
Messages
46
Location
Munich
I am looking for guidance to help fringe reception of vhf marine transmissions. The distance I am trying to span is around 18-20 miles and I believe there is a slight hill breaking the line of sight along the way. I am limited to attic mounted antennas (wood, shingles, no metal). I am using runs of commscope rg6 that spans 70-100 feet depending on location in the attic. Loss is around 2-2.25 dB per the data sheet. I am working with a few radios: RS Pro 2032, Pro 95, PSR 800. With my attic mounted tram discone antenna I cannot receive any maritime signals.

As a test case I built a 5 element yagi that spans 150-165 MHz. It was designed for 75 Ohm to match the rg6 and at 157 MHz it is modeled at 9.5 dBi realized gain. The cable run is around 100 ft. I have no way to verify the gain but it’s measured vswr at the antenna input matches up nicely with the model. Testing the front to back ratio against NWS transmitters seems reasonable.

I mounted the yagi and pointed it in the desired direction. I now receive some signals including a coast guard station, a commercial land-based maritime transmitter, and very limited ship transmissions. For the signals I do receive I can tell what they are saying but the signals are generally weak and noisy. I am not expecting too much based on my location and installation limitations but I would like to see if I can clean up the signals I do receive and possibly get some more.

I am considering my options to try to improve reception. Ideas:

  • Increase gain of yagi by 2-3 dB
  • Add preamp and possibly FM trap at antenna. I’ve never worked with these before.
  • Lower loss coax - Running new coax is a pain so I would like to avoid it if possible. Also, I cannot easily run larger than ~0.25” diameter given the routing needed.
  • Anything else?

I am seeking advice for my situation and for prioritizing what to try next. Thank you.
Yagi aerial good choice but corner reflector aerial allows wider beam width pattern. I know there is an aerial that is vertical and has a grid behind it that increases gain and has much wider beam width. Also corner reflector and vertical grid aerials are usually very expensive and are not designed for hobby market. The CRV-1617 corner reflector aerial claims 10db gain.

www.antennaproducts.com

CRV-2.jpg
 

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JoshuaHufford

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Bringing the radio up the the attic is a great suggestion. I will try that when I get a chance. As you point out, it should help answer the coax question.

I just checked and my coax is Commscope F677TSVV. The data sheet shows 2 dB / 100’ at 85 MHz and 2.9 dB at 187 MHz. So probably 2.7 dB loss for my run at 156 MHz. For reference, and equivalent LMR 400 run is around 1.8 dB, which is about 20% less loss. Not a huge difference.

Regarding the radio, I am running tests on a couple few older RS analog scanners and a PSR 800. I do see more reception variation among them than I was expecting. I will take a closer look at the specs to see if I can tie them to the differences I hear. Perhaps there is something to be gained with a radio with better marine band sensitivity. I plan to dedicate the antenna and a radio to marine band reception so I would be fine with getting a radio that is optimized for marine band only.
I will order a preamp and some filtering to see if that helps. I have some flamethrower FM stations (~-45 dBm at radio input) in my area so I think an fm filter before the preamp is needed. I plan to go with the HPN-30118. The AIS filter you found looks interesting and I will keep it mind. If I go with an fm filter before the preamp, then I do not the AIS filter after the preamp would provide much benefit in my situation. But it is inexpensive so I may it get it as well.

I was leaning towards the mini circuits ZX60-P105LN because the gain is not too high at 14 dB, low NF, and decent 1dB compression. I will take a look at the PGA103+ before I place the preamp order. Either way, as you point out, I need to get an attenuator in the path. Thank you for your reply.

Are you sure your coax is RG-6? I'm using the Times Microwave calculator and I would think it is pretty accurate. They are showing 2.7db loss at 85MHz and 4.1db loss at 187MHz for RG-6, that is a pretty large difference.

I've had great results with older Motorola M1225 Radius and CDM radios, if your watch you can usually find them used at good prices, however it will need to be programmed for your needs.

How many channels do you monitor/scan?

I've heard good things about the mini circuits preamps but I haven't personally used one.
 

prcguy

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So Cal - Richardson, TX - Tewksbury, MA
Beam width and gain go hand in hand, you cannot have wide beam width and high gain. If you compare corner reflectors and Yagi's with the same gain, you will find they have nearly identical 3dB beam width. Those are laws of physics you can't change.

For the OP, a preamp at the antenna can help but be careful on the gain, you only need enough to make up for feedline loss and maybe a little more like 3 or 4dB at the most. More than that and you will have other problems creep in. A commercial Yagi with known gain is not a bad idea as you have no idea how your home made antenna is performing. It could meet specs or it could be down several dB or more. More gain is good if you can build it or afford it. I use a wide band Yagi here made by Sirio, model WY140-6N and I love it. It covers 140 to 160MHz continuous, (they have a 155-175 version) with 8.35dBd or 10.5dBi gain.

I have the parts here to make a perfect setup for long distance marine band listening, the Sirio Yagi, a DCI sharp band pass filter that only covers 156 to 162MHz and various medium gain high level preamps. The DCI filter is hard to come by but the other parts can be had off Ebay.

BTW, the MiniCircuits ZX60-P105LN preamp without a filter could be trouble if you have any transmitters nearby, here it overloads really bad when used with a Discone. You would also have to attenuate by a good 6dB or more to get the gain in the right place.



Yagi aerial good choice but corner reflector aerial allows wider beam width pattern. I know there is an aerial that is vertical and has a grid behind it that increases gain and has much wider beam width. Also corner reflector and vertical grid aerials are usually very expensive and are not designed for hobby market. The CRV-1617 corner reflector aerial claims 10db gain.

www.antennaproducts.com

View attachment 88230
 

MDScanFan

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There are a lot of flavors of rg6 and I do not know what flavor the times microwave calculator is assuming. The numbers I listed are directly from the suppliers data sheet for F677TSVV.

I started by monitoring all marine frequencies to see what I get. I have been hearing traffic on about 8 frequencies.

Are you sure your coax is RG-6? I'm using the Times Microwave calculator and I would think it is pretty accurate. They are showing 2.7db loss at 85MHz and 4.1db loss at 187MHz for RG-6, that is a pretty large difference.

I've had great results with older Motorola M1225 Radius and CDM radios, if your watch you can usually find them used at good prices, however it will need to be programmed for your needs.

How many channels do you monitor/scan?

I've heard good things about the mini circuits preamps but I haven't personally used one.
 

MDScanFan

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I went the home brew route because I had material on hand, experience designing/building them, and I had no idea whether I could get any marine signals with my compromised location and installation constraints. I did not want to “invest” in a commercial antenna just yet. Now that I confirmed I can get some signals I am trying to prioritize what to try next.

The commercial yagi’s you pointed out are definitely worth considering. As you mentioned, I do not know how well it is performing and I have no easy way to confirm. I did a tolerance study and it seems fairly resilient at these frequencies to expected build variation. But I can’t be certain I am not losing a dB or so in the end.

Regarding the sharp band pass filter... I know I need to beat down fm bcb signals before the preamp. Do you think there is much value in adding a pass band filter after the amplifier as well? Such as the one Ubbe referenced above.

My current plan in order:
- listen to scanner at antenna feedpoint
- buy fm filter, good preamp, and attenuator. Place them in that order with the fm filter on the antenna side.
- tack on two more directors to the yagi and see if it helps. This is easy to do and the model predicts a 1.8 dB gain increase.


For the OP, a preamp at the antenna can help but be careful on the gain, you only need enough to make up for feedline loss and maybe a little more like 3 or 4dB at the most. More than that and you will have other problems creep in. A commercial Yagi with known gain is not a bad idea as you have no idea how your home made antenna is performing. It could meet specs or it could be down several dB or more. More gain is good if you can build it or afford it. I use a wide band Yagi here made by Sirio, model WY140-6N and I love it. It covers 140 to 160MHz continuous, (they have a 155-175 version) with 8.35dBd or 10.5dBi gain.

I have the parts here to make a perfect setup for long distance marine band listening, the Sirio Yagi, a DCI sharp band pass filter that only covers 156 to 162MHz and various medium gain high level preamps. The DCI filter is hard to come by but the other parts can be had off Ebay.

BTW, the MiniCircuits ZX60-P105LN preamp without a filter could be trouble if you have any transmitters nearby, here it overloads really bad when used with a Discone. You would also have to attenuate by a good 6dB or more to get the gain in the right place.
 

Ubbe

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Yagi aerial good choice but corner reflector aerial allows wider beam width pattern.
That corner reflector are compressing the loob sideway so it will be very directional, but at the same time, as it is a single dipole, will have its loob pointing up in the sky and down in the ground as there's no reflector for those directions, that will be a total waste. Try to concentrate on antennas the compress the signal vertically at the horizon and not up in the sky or down in the ground where there is no point in wasting precious antenna gain.

/Ubbe
 

JoshuaHufford

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There are a lot of flavors of rg6 and I do not know what flavor the times microwave calculator is assuming. The numbers I listed are directly from the suppliers data sheet for F677TSVV.

I started by monitoring all marine frequencies to see what I get. I have been hearing traffic on about 8 frequencies.
Well hopefully the specs for your coax are accurate. Please let us know the results after you test up in the attic. I think you are going the right direction with your process.

BTW if you only are getting traffic on 8 channels I would be looking into a VHF Motorola 20 Channel 1225 Radius.
 

hill

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Going forward it may not be doable to receive more on the marine band from your location. If you have some hills between your location and the water it may be hard to get your indoor antenna to see over them. I know that not what you wanted to hear on this Forum, but need to be realistic here. If you receive anything it will most likely be the large ships with the higher antennas or land stations like the Coast Guard. In my local CG Sector their antennas for the different sites range from 200' to around 600'. Most small pleasure vessels have low antennas and really don't have much range on VHF.

Would think a real VHF marine radio would work the best. Scanners are made for a broad range of frequencies and the marine radios is made for just a small ranges of the VHF frequencies in the marine band. A good Standard Horizon or Icom work well. You use an marine radio just to listen and never transmit with it.
 

MDScanFan

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I completely understand and agree with the first paragraph. I don’t have expectations to dramatically change what I am getting. I would be happy to improve the clarity of what I do get and maybe eek out a few more signals if possible. I realize getting pleasure craft vhf is not going to happen. While listening today I was able to get the coast guard, numerous large ships, and some land based businesses. I found the traffic interesting.

I started a separate thread in the marine forum regarding a radio recommendation if i end up going the marine radio route. I need to do more homework on that topic.

Going forward it may not be doable to receive more on the marine band from your location. If you have some hills between your location and the water it may be hard to get your indoor antenna to see over them. I know that not what you wanted to hear on this Forum, but need to be realistic here. If you receive anything it will most likely be the large ships with the higher antennas or land stations like the Coast Guard. In my local CG Sector their antennas for the different sites range from 200' to around 600'. Most small pleasure vessels have low antennas and really don't have much range on VHF.

Would think a real VHF marine radio would work the best. Scanners are made for a broad range of frequencies and the marine radios is made for just a small ranges of the VHF frequencies in the marine band. A good Standard Horizon or Icom work well. You use an marine radio just to listen and never transmit with it.
 

MDScanFan

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That’s thinking outside the box and will keep it in mind. For now I will play with my setup to see how much it can be improved with a little bit of work. I do know people who live in a perfect spot for reception. However, none of them are radio fans.

One thing I will try in the near future is to visit a good site with my handheld and see what I am missing for marine traffic.

It’s one of those things where if you don’t know what you are missing then it does not seem too bad. I went from not being able to listen to anything to hearing some limited traffic. So I am happy. Once I listen to what is out there (live feed or handheld from good location), then my home reception will be disappointing. Ignorance is bliss.

Do you know anyone that lives closer to the target area you want to receive that could host a remote controlled receiver and antenna? Then just connect to that over the Internet and your done.
 

MDScanFan

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I brought a radio into the attic and checked signal quality with a 3’ coax run. With my limited checks of a couple channels I did notice some signal quality improvement. So I do think the 100’ coax run is having an impact. If I was smart about it I would have brought a 100’ spool of coax with me for an apples to apples with me for the test - lesson learned for next time.
 

MDScanFan

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Can I please get some feedback on the configuration I plan to try. Right now I use the yagi and coax. I plan to try:

  • Yagi (home brew)
  • FM (HPN-30118)
  • Preamp (ZX60-P103LN), ~24 dB gain
  • 100’ RG6 (Likely 2.5-3dB loss)
  • Attenuator (HP with 0-20 dB atten)
  • Limiter (HP 5086-7284; 10W max in; 10 dBm max thru)
  • Receiver

Everything but the amp has been ordered. I plan to use this for marine band reception tests. After that I will try the components with my airband setup that uses a separate scanner and a discone.
 
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