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+--- Thread: Blue Classic and Ham Radio possible interference (/showthread.php?tid=3956)
Blue Classic and Ham Radio possible interference - KM4LFT - 2024-09-30
Our club is hoping to install a Blue Mini with filters on top of a 185 foot tower that's shared with ham radio antennas. Ham radio transmitters are all less than 100 watts over the range of 3.5Mhz to 440Mhz. Can anyone share their experience or expectations for possible interference on the Blue Mini from those transmitters? Thanks, Larry, Georgia
RE: Blue Classic and Ham Radio possible interference - mendip_defender - 2024-09-30
Ask
https://www.blitzortung.org/en/station_list.php?&stations_users=1&selected_numbers=2234
aka
http://www.gb3bs.com/
As they have experiance.
RE: Blue Classic and Ham Radio possible interference - cutty - 2024-09-30
(2024-09-30, 13:49)KM4LFT Wrote: Our club is hoping to install a Blue Mini with filters on top of a 185 foot tower that's shared with ham radio antennas. Ham radio transmitters are all less than 100 watts over the range of 3.5Mhz to 440Mhz. Can anyone share their experience or expectations for possible interference on the Blue Mini from those transmitters? Thanks, Larry, Georgia
That's a lot of trouble for a magnetic array that even works in a basement. I wouldn't go to that extreme. It's not necessary. Hams on board will respond as appropriate, but I'd highly recommend abandon the mast mount and simplify. Also removes the preamp assy from EMF produced by 'near misses'....
RE: Blue Classic and Ham Radio possible interference - mwaters - 2024-09-30
(2024-09-30, 13:49)KM4LFT Wrote: Our club is hoping to install a Blue Mini with filters on top of a 185 foot tower that's shared with ham radio antennas. Ham radio transmitters are all less than 100 watts over the range of 3.5Mhz to 440Mhz. Can anyone share their experience or expectations for possible interference on the Blue Mini from those transmitters? Thanks, Larry, Georgia
Whenever I transmitted on the 75 meter ham band, it completely overloaded my Blitzortung lightning receivers.
You don't need to put them up high. My antennas worked best at ground level and in my basement.
RE: Blue Classic and Ham Radio possible interference - VA_LM_Blue - 2024-10-01
(2024-09-30, 13:49)KM4LFT Wrote: Our club is hoping to install a Blue Mini with filters on top of a 185 foot tower that's shared with ham radio antennas. Ham radio transmitters are all less than 100 watts over the range of 3.5Mhz to 440Mhz. Can anyone share their experience or expectations for possible interference on the Blue Mini from those transmitters? Thanks, Larry, Georgia
There is no way to guess how a Blue Mini will behave in that environment. IMHO.
My system blue receiver sits in the radio room only a few feet from rigs, feedlines, coax, etc. It is not grounded to the HAM station ground as recommended. The 3 ferrite bar antenna, horizontal delta shape, sits on the floor in a bedroom down the hall, a few feet above the basement crawlspace, real ground. Rarely does it go crazy when I transmit, up to 500w. It does seem to not like 80m when transmitting over 100w sometimes.
There is little reason to put the antenna or mini on a tower. The e-field antenna--maybe. I have not used my e-field components so have no experience. There may be issues with long cable runs.
You want your antennas in as quiet a place as possible. Use an AM/LF portable radio and search for as quiet a place as you can find and that is probably where you want to put your antenna. Use a good, clean, low-noise power supply and some ferrite chokes on the cord if needed.
RE: Blue Classic and Ham Radio possible interference - mwaters - 2024-10-01
(2024-10-01, 00:23)VA_LM_Blue Wrote: .
There is little reason to put the antenna or mini on a tower. The e-field antenna--maybe. I have not used my e-field components so have no experience. There may be issues with long cable runs.
Yes, any E-field antenna should be higher. Over your roofline. I had one about 20 feet high, which is what was recommended here.
I don't know —and I don't think anyone does— how an E-field antenna would perform at greater heights.
There will indeed be issues with long coax runs, namely, voltage drop! RG-6 cable has a thin layer of copper over a steel core. The DC resistance would be so high at 185' that the amplifier would not work. Perhaps if you used RG-11. I have some similar F-11 with an aluminum shield; the center conductor being copper over an aluminum core. But it's been a long time since I looked up the ohms per foot and calculated the I²R losses.
Another thing to consider is if the metal tower would affect it. It could couple to it.
I say, forget the tower. Put all your lightning antennas at a distance from it. Later, you can elevate the E-field antenna and see how it works.
RE: Blue Classic and Ham Radio possible interference - cutty - 2024-10-02
(2024-10-01, 21:53)mwaters Wrote:(2024-10-01, 00:23)VA_LM_Blue Wrote: .
There is little reason to put the antenna or mini on a tower. The e-field antenna--maybe. I have not used my e-field components so have no experience. There may be issues with long cable runs.
Yes, any E-field antenna should be higher. Over your roofline. I had one about 20 feet high, which is what was recommended here.
I don't know —and I don't think anyone does— how an E-field antenna would perform at greater heights.
There will indeed be issues with long coax runs, namely, voltage drop! RG-6 cable has a thin layer of copper over a steel core. The DC resistance would be so high at 185' that the amplifier would not work. Perhaps if you used RG-11. I have some similar F-11 with an aluminum shield; the center conductor being copper over an aluminum core. But it's been a long time since I looked up the ohms per foot and calculated the I²R losses.
Another thing to consider is if the metal tower would affect it. It could couple to it.
I say, forget the tower. Put all your lightning antennas at a distance from it. Later, you can elevate the E-field antenna and see how it works.
Just a 'qualifier'...
Blue Mini is a 2 channel H field system. There is no E probe channel in Mini. E field is incorporated only in System RED (3 ch) and System Blue (Max)(1 ch).
Aside:
For 'E field'... Richo (developer) once stated that there was NO limit on coax run for distance of Efield... as far as delay of signal, because of the type of sensor (probe). As MikeW mentions at some point the coax would drop enough voltage to 'turn off' the preamp. Richo told me, with a grin emoticon, "A mile? Couple of Kilometers"? We suggest a 100 meters max E coax install , however.
Power: DC resistance of a good Coax cable might be <2 ohms /1000Ft, ( center + shield) . So one mile would be 10-11 ohms DC resistance. Pure copper triple shielded if you can get it... actually, that's more for signal purity and integrity than resistance....
Signal: Remember E field isn't an antenna. It's a probe. Should be isolated from ALL structures. 2-4 meters, minimum, above earth is good. No real need to be much higher. Mine are about 4-5 meters on fiberglass mast.
Re: cable
General rule of thumb: If a 75 ohm coaxial cable is connected to a source with 75 ohm impedance and the output of the cable is connected to a 75 ohm resistive load, all energy is transferred from source to load (zero reflected energy). That's one reason the E preamps actually work 'at a loss' of about 4-6 db... it's a very sensitive circuit.
3 to 300 kHz (with dominance <30kHz) such coax is virtually two conductors separated by an insulating material, and not a 'transmission' line. Even though it's characteristics can be considered part of the 'filtering''matching' network for the 'Capacitance' probe E channel assembly, for our purposes as 'operators', and our target spectrum, it could be considered a DC RC circuit. Remember, we're trying to filter out >300kHz anyway, so we don't care if they 'make it' or not. (Note that later firmware and design have 'cut' that upper limit back to about 220kHz because of ADC sampling frequency.)
Such is NOT TRUE for H preamp... Excessive, and/or poor quality unshielded net cable can even can generate noise and uncompensated / unexpected signal delays. 30 meters maximum is the rule for H field.