Ham Radio - Revisiting the PA0RDT Miniwhip active RX antenna.
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- เผยแพร่เมื่อ 16 ก.ค. 2024
- I wanted an always available RX antenna for SWL without any setup. Then I remembered that I had a Miniwhip. Here's how I installed it on the RV and some testing.
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critical thing to realise is that the whip is an e field probe; height is very important but your installation has very little. Also, the whip must be above the mounting metal/body of your vehicle. if you raise it higher, you will get substantially better results. ground the pole or sheath of coax.
1. I remember thunderstorms when I lived in Arizona. They were the worst I have experienced. 2. It's nice to know of hams who are also SWLs.
I've been using my active mini-whip receive antenna for about eight years and like it. I mounted mine in a 3" SCH 40 section of PVC pipe, attached to 2" SCH 40 PVC eight feet long attached to my house with standouts. The antenna is at about 24 feet (4' above the house) and the coax is grounded to a 8' rod and lightning arrestor. I use an MFJ 4117 switched bias tee. The noise floor stays pretty low. Thanks for your great videos!
As an experiment consider the following. 1. Use an above ground radial rather than a ground rod. 2. Make a small dipole antenna as opposed to a vertical antenna. 3. Try a small loop antenna rather than a vertical or dipole antenna. If you're adventurous, make a small tesla coil & 'temporarily' power it from the static electricity from your doublet antenna.
Just the simple comparison at the end of the video between the mini-whip and chameleon was very useful.
Thanks for the video.
Mine is 6' above the tallest peak in the roof, approximately 35' off the ground, I have the coax shield tied to a ground rod.
My radio is a Kiwi SDR and it's just on my LAN at the moment. It runs very nicely in a Chrome browser on my iPad.
My impression of the mini whip is that it's really pretty good for casual SW and broadcast listening. It seems better below about 20MHz. I can regularly pick up broadcasts worldwide and the AM dxing can be very good. It's my only antenna right now and it's working well for my needs.
Nice insight Kevin
Nice test of this interesting antenna. I am going to give it a try. It is even supposed to work down at VLF !
No to start a big lightning war but a friend of mine (who was in professional 2-way work) had a copy of a seminar that (supposedly) was comprised of the latest in 'what-to-do' lightning practices. The conclusion (which I see as both intuitive and counter-intuitive) was that all unused antennas should be grounded. The reason given, was that research showed that the feelers the lightning initially puts down, looks for objects that it can raise or change their potential; so if it can't raise it, it moves on so-to-speak. Anyway, I can see it two ways: obvious what was just described but the old-school of thought is that lightning is looking for a good ground---anyway, I ground everything when not in use. So, even if you have an antenna with the coax (etc.) rolled up, you might want to still ground the feedline. Great video and 73...
I remember seeing a video which may have been on TH-cam about them adding a six inch plus piece of copper wire onto the end of the square on the circuite board & this gave him an improvement but didnt recommend increasing it any longer.
Power lines make AM noise. That's the reason that they did away with the electric trolleys in the 1940s-1950s. Nobody in town could listen to their giant wooden tube radios with all the wires overhead. It's still evident when you're listening to broadcast am on the car radio and drive under transmission lines.
Digressing off topic, the new LED bulb traffic lights give off a LOT of radio noise - you can hear them sitting at a light on broadcast AM, once you drive through the intersection reception comes back. I figured that out because I hung a used traffic light in my garage/shack and couldn't pick up squat on HF when the traffic light was on.
Cool antenna idea, even though vehicle antennas are almost always a compromise - you have to work with what you have.
Thanks again. Careful if you visit Port A and Rockport. West Nile virus is already active. But we did leave plenty of sand for you.
I've had great success at LowFER communications. The voice of experience says that you NEED a virgin ground for good reception very far below the AM broadcast band because the ground IS part of the antenna.
As for the size of the Mini-whip, my experience ( and experiments) indicate that any antenna longer than about 4 feet when used on sub-500 kHz frequencies merely picks up more noise, not more signal.
The critical variable is WHAT frequency we are talking about. Signals do not behave the same at all frequencies. Longwave has its own behaviors just as 2 meters is different from 80 meters.
Frankly, the Mini-whip was designed for the lowest frequencies, where it excels. BTW, I know nothing about the designer of that antenna, except that he knows what he's doing at LF.
BTW, you are doing the antenna a great disservice by mounting it beside the body of the RV. Mount your other antennas 3 inches away from the body of the RV and you will see their performance go to hell, too.
It's above the body of the RV, not beside it. At the top of the tube, above the ladder. And after a bit more use, it's working better than I thought initially. Maybe not the best it could, but it's fulfilling the intended task. Providing me an RX antenna that's always available.
just a thought could you not use a 3/8th bolt through the cap in the same maner as you have and when you want to you could screw in several differnt antennas depending on what you want to listen too .
I tried this once and it wouldn't pick up anything, on the other hand the MLA-30+ Loop Antenna works pretty well.
hy just watched your brilliant video, Q the power going up coax to amp, do you have to wire this to the 3v vin tabs or does the power from coax automatically operate the amp?
The circuit boards I have seen are all powered through coax. I have not seen preamp boards with a V_in tab. Therefore, let me describe what to look for on your preamp board so that you can determine whether your unit can operate with power through coax. Pause the video at 0:47, switch TH-cam's video quality to 1080p, and look at the right end of the "low-noise broadband amplifier." Just above the coax connection, you can see a small black "can" labeled L1. That inductor blocks RF and passes DC from the coax to the amplifier, while capacitor C3 blocks DC and passes RF from the amplifier to the coax. If your unit can operate from power over coax, it must have those two components. Many mini-whip preamps have two inductors, in which case the inductor connected to the coax may be labeled L2. If your preamp has a V_in tab, it almost certainly is connected to the end of the inductor that is not attached to the coax.
Just read what the original designer tells you to do and it will be fine.
MiniWhip is not meant to be for shortwave but for frequencies below 3 MHz.
MiniWhip relies on signal to noise, not big signals.
etc.
Read the manual from the original designer.
Thanks for the demonstration.
I wonder how it would work if you attached an old car antenna from a salvage yard to the active antenna. Or an old whip from a 2m or cb antenna. Just a thought. Let me know if you try it and if its a success or a failure.
I've done that in a previous video, back when I first got it.
Can the bias-t of the RSP1A drive the Miniwhip? Nice video
Yes. I've done it back when I first played around with it.
Did I relate the story of my Diamond discone here? Short version: I was installing one at home on a cool, overcast day. All went well, until I put on the BNC connector in the shack. I was getting a slow, repetitive spark from the center pin to the grounded contacts around it. I first wondered if the coax was somehow contacting an electrical connection in the attic. Turns out, it was just the static of the wind, moving past the hot side of the antenna outside. A home-brewed 100k resistor from hot to ground in an inline project box took care of that. I hated to think what that charge could have done to my receiver!
I've been able to draw sparks from several types of antennas when there's a charge in the air. Usually when storms are passing within a few miles. I disconnect my wires when there's weather moving through.
It also seems to happen more often at higher altitudes since you're closer to the upper layers of the atmosphere.
@@loughkb I was just in good old pancake-flat Southern Florida. But that was a static wake-up call for sure.
@@unklewink Florida, the lighting capitol of the states.
You'll get a lot of that charge there.
I've been in Arizona for awhile and in about a month, monsoon storm season starts. I'll have the antennas disconnected more often than not.
@@loughkb I have felt the wrath of lightning. I was disconnecting a 450 ohm antenna feedline from my rig to protect the rig, as a thunderstorm approached. Lightning hit a neighbor's tree at that moment. Knocked me on my... you get the idea!
Thank you for your video. I have a bad experience with Mini Whip, may some body can help me. I bought recently from Amazon a miniwhip developped by RA0SMS but after connection to my antenna, No signal appear .... even if the led is on in the intermediate box .... I am very disappointed ... If somebody can give some good advise
Have you tried adding a wire to the antenna patch? Or would that overload it?
I did in a previous video back when I first got it.
Did you ever try attaching wire onto the antenna plate?
Yes, made a small difference.
Has anyone even thought about installing a BALUN into the front of the PA0RDT so it will work as a dipole,
why not just add a short CBm antenna to the mini-whips pcb board direct with a coax from a mount on the railing to the ladder. and use the ladder as counterpoise... that should work and just look like a CB antenna for the RV
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Your 12 v dc power supply... what's the amperage levels (or max. amp. level you would go), that you can use on your active antenna? Some 12 vdc power supplies give off, 1 and 2 amps.? Would that be too hot for the circuit?
Current doesn't work like that. A power supply may be capable of providing 5 amps of current, but the circuit will only draw as much as it requires.
@@loughkb I sort of figgered tha, but doesn't harm to ask. I have a new active powered antenna for receiving SDR signals on computer. Plugged the 12 V DC power supply in, and the first capacitor ( just before the Z diode) in the circuit, and his is showing signs of heat by smoking and a small burn mark. Must be Zener was shorted when circuit made up at factory. Getting very high ohm readings in both direction, not just in one direction. Appears there's a short to Gnd..
You don't need a ground wire, just a ground plane. Mount it on a metal pole.
It's presently living atop the metal ladder on the back of my RV. Working pretty well. It's an always available RX antenna that takes no time or effort to put up.
Kevin, I am trying to get my malahit to work with gqrx and I am not seeing the airspy settings in your video. I am behind the curve on going open source on a raspi. Can you give hint as to how To get it to work. Perhaps do a video on configuring the malahit to work. Please?
I hadn't looked into that. I didn't know the malahit would provide I/Q signals over USB.
@@loughkb from what I understand in windows world the malahit can be controlled and will work with the computer via the USB connection. I'm not familiar with the malahit completely yet. It was given to me by another ham. He said he wasn't having any luck with it and was tired of playing with it. It is a chinese clone.. I opened it up and after some online research discovered it was missing a FRAM chip FM25W256-G. This chip is looked for by the upgrade firmware and if it doesn't find that chip, the software stops in a loop looking for it and it acts as though it is bricked. I bought a few of those chips and installed one in my malahit and upgraded the firmware to 1.10a and it worked. I know the malahit requires the upgrade software to make it talk through the usb cable. I have a raspberry pi 3b at my station and I pieced together my OS starting with debian buster command line, the lite version and then added the rest of the parts to customize it a bit according to some directions I found online. I added a GUI and a bunch of ham software. It recognizes the malahit being connected as near as I can tell but it's not showing up on the list in gqrx. I'm not sure if it's a driver issue or something else. I may try one of the ham specific OS for pi that you reviewed.
@@kd5inm Ok, I think I follow.
Through the USB connection, the radio creates an audio device. Any program that can record audio should be able to select it as an input. For example, FLDigi for decoding various digital HF modes.
It also creates a serial port device and can use that for basic rig control through programs like FLRig.
GQRX is a program designed to take in I/Q signals from SDR receivers like the airspy, sdrplay and such. Where the hardware is just acting like a digital sampler for RF and the software does all the demodulating stuff. GQRX is the radio, the hardware is just an RF sampler.
So two different things.
The malahit does all the sampling and demodulation already, only outputting audio.
@@loughkb OK, I understand. How were you getting GQRX to work with the malahit? Or did you have GQRX connected to another device? I was thinking you had the malahit connected for GQRX. Or am I mistaken? I appreciate your patience and kind instruction on this as well as your videos. I have been watching and subbed for many years..
De KD5INM
@@kd5inm I don't remember using the malahit with gqrx. What did you see that gave you that idea? Which video? I'll go look at it and attempt to explain what's going on.
What sdr receiver are you using it goes low
An Airspy discovery HF+
@@loughkb Welp i have seen it everywhere better get out my wallet
A low of 9khz is very very good
Have you sold your house now and the RV is your permanent home? How do you earn a living Kev?
Best wishes to you and always enjoy your videos.
Kind regards,
Chris G0VOE in Somerset (Southwest England).
I sold the house almost three years ago when I left in the RV.
I earn my survival via these youtube videos and the support of my patreon folks.
Wow! Glad it all worked, keep the videos coming, they're always good to watch.
Great video and info.
I use it for SWL and as a pick up antenna for my X-Phase II QRM killer. For me it works best when installed 30 cm above above my tin roof which is not grounded (but connected to the ground of active antenne).
The MiniWhip It is also used on the WebSDR of the university of Twente ( websdr.ewi.utwente.nl:8901/ the mother of all websdr's) for years (there is technical details info writen by Pieter-Tjerk de Boer PA3WFM on www.pa3fwm.nl/technotes/tn09d.html ) .