Keep in mind that your receiver can be easily overloaded with a full spectrum of signals from the mini whip antenna. Especially strong AM broadcast station can cause a lot of intermodulation. Thanks for sharing you experience.
I made an elongated version of the miniwhip to fit into a 1 foot piece of PVC 3/4 inch pipe. A pl259 plug's shell fitted snugly into this and the other end was capped. A simple bias-tee was made for inside the car, which had a SO239 connector antenna mount already on it. Getting away from the local noise, the results have been amazing. When first tried, I thought the antenna must not be working because there was no background noise, but then I tuned across a stonking great signal on 160. I mention this because I've never heard of anyone trying the PA0RDT on a mobile mount. I can confirm it works extremely well, fed against the car bodywork. I note that the Web SDR at the university of Twente uses a miniwhip, grounded at its feedpoint to the metal roof. Opinions vary on whether to ground the antenna end of the feeder braid or not, but my experience suggests you should, if you can. Thanks for the videos, 73 de G0IFI
There's a few restrictive factors here now I'm taking a close look at this experiment. No.1 is the small width of the cut in the ground plane between the circuit and the part of the copper forming the antenna section on the board. This will negatively impact the performance as there is going to be significant capacitance between the gate and ground at the input of the JFET. The MPF102 also has a little higher gate capacitance than the J310. This all contributes to act as a capacitive divider for the very short antenna terminating the extremely high gate input impedance of the FET... a few pF really matters here when we're dealing with megohms! The use of a 2N2219 is also a handicap as it will not be anywhere near as 'hot' as a 2N5109 in terms of its RF performance. I have a lot of 2N5109 as well as 2N4416A JFETs (perhaps lower gate capacitance than the J310) and this weekend I'm going to investigate this circuit myself and seek to squeeze every last ounce of potential out of it. I plan to take it, as well as my homemade active loop antenna to a local park with no powerlines for hundreds of meters and make performance comparisons
Clever tip on using the loop tuner in conjunction with the adjacent mini whip. Induction and capacitance can produce interesting results with some radios. I'll try that on mine.
Thank you for posting this video. I have struggled with an active mini whip ~25 feet off the ground. The noise is terrible and antenna unusable. I have the RA0SMS version of the PA0RDT - it produces 10 KHZ 'spikes' across the entire HF band. I never thought about attaching it to a stick and moving it around the back yard - brilliant. What a simple task that I completely overlooked. I'll give your process a shot today to see if I can get a usable signal. As it is, @ 25 feet in the air with no obstructions, it is simply not usable.
Great video and I have been building and experimenting with the mini-whip myself. What I do miss in the video is the earth connection. If you want to get it in the clear then I found you need to bring the earth connection to the mini-whip. This shows in your video when you hold the whip close to the ground. Mounted on a 12 meter fiberglass pole with a separate earth going up to the whip I had excellent results.
Just moved into a flat where wire antennas aren't possible. I built one of these exactly as per the original circuit by RDT and it's astonishing. I think yours shows a better S/N ratio near the ground because you're giving its "earthy" side a capacitive coupling to ground. I ran a wire from the braid at the feedpoint of mine, connecting it to a water pipe and the noise dropped by 6 s-points. I'm going to ask the landlord nicely if I can get the thing mounted up on the roof, 4 stories up. Should be interesting. It's remarkable just how much signal this simple little thing does pull in. Thanks for another interesting video. 73
IIRC on this circuit it's really a matter of having it grounded to earth since that gives it a better amount of potential difference between the patch which is connected to the JFET and the feed line. I know that i've played with a version of a whip amp from Charles Wenzel which had similar characteristics where if I touched a wire attached to circuit ground the signals would peak and the noise levels would dramatically reduce on my SDR software. All this was with battery power as you did. I'm not an electrical engineer or a physicist but I think having any kind of ground improves the amplifier (even just some coiled up coax attached to circuit ground produces similar results in my own tests).
Hi.Peter. It looks to me like the sort of receive "antenna buffer" that would work best with a telescopic whip of around 60cm. You could slide it in then to note the results with different lengths. The comments about grounding seem valid too. Mounting it on top of an aluminum tube which is connected to the RF ground of the PCB will probably much improve performance, especially if the tube is then grounded also. It probably would be a great general purpose monitoring antenna, although for MF (and even for HF) my preferences are towards tuned loops fed into a differential antenna amplifier converting the high loop impedance down to one suitable for feeding the RX
I'm experimenting with a mini whip designed to be lower, compensating for the lower signal level that comes with a smaller distance between points within the electric field (V=E*d and whatnot) by a third transistor stage in the middle designed for voltage gain
Thanks for this video Peter, it inspired me to do something similar with a Ramsey Electronics SA7 preamp kit although I had good results at 5m above the ground and with the outer coaxial cable shield uncoupled. I just need to progress to the DC injection stage instead of using a 9v battery :)
I have built mine, but I am still using 9 volts 200 mA and when I tried to use 12 volts 200 mA the 2N4124 was becoming warm. What's the proper voltage and current, and how do I get that type of power source?
Sorry to hear that, but don't give up. Get a good earth connection, place it far away from objects outdoors and use the attenuator on your rig if needed. I did hear a lot more with this whip than with a 20 meter vertical.
To function, the PA0RDT MiniWhip Antenna *needs* proper Grounding.. Without (really) Grounding it, this Antenna-Type is almost useless. So it is not the best "portable"-Antenna. However, using it the Way, it is used in this Video, the Antenna seems to be a good Indicator for what would be a good Ground and what would be not.. :/
You are definitely right about that. Grounding the braid of the coax kills most of the background noise. He isn't giving the antenna a chance floating it like that.
Ohh dear! that antenna should be grounded in order for it to work properly! When its installed properly its capable of receiving the Russian Alpha signals at 12khz and many submarine comms transmitters from around the world from Melbourne
Hey mate, check this out. Seems the Australian Government department of defense thought that the miniwhip concept was worthy of consideration, although theirs is conceivably more detailed and involved. I found it interesting though. No free lunch, earth it well 😉 DST-Group-TR-3522.pdf
vk3ye Peter, my understanding is that these antennas work best with a suitable groundplane and a good example of it use is : websdr.ewi.utwente.nl:8901/ where he says "Such an antenna only works well with a good grounding; ours is on top of a 20m high building, the upper part of which is all metal."
An slightly alternative design is the one from PA0NHC (members.ziggo.nl/nvrecording/nhc/Projects/Miniwhip/20121025miniwhip.htm). Is less susceptible to IM and produces a slightly more moderate signal output.
A very poor test of a mini whip. what grounding arrangements did you have? Try a Chinese unit and get it up high in a quiet area. It outperforms amplified lops when built and used correctly, not waved around randomly[
Keep in mind that your receiver can be easily overloaded with a full spectrum of signals from the mini whip antenna. Especially strong AM broadcast station can cause a lot of intermodulation. Thanks for sharing you experience.
I made an elongated version of the miniwhip to fit into a 1 foot piece of PVC 3/4 inch pipe. A pl259 plug's shell fitted snugly into this and the other end was capped. A simple bias-tee was made for inside the car, which had a SO239 connector antenna mount already on it. Getting away from the local noise, the results have been amazing. When first tried, I thought the antenna must not be working because there was no background noise, but then I tuned across a stonking great signal on 160.
I mention this because I've never heard of anyone trying the PA0RDT on a mobile mount. I can confirm it works extremely well, fed against the car bodywork. I note that the Web SDR at the university of Twente uses a miniwhip, grounded at its feedpoint to the metal roof.
Opinions vary on whether to ground the antenna end of the feeder braid or not, but my experience suggests you should, if you can.
Thanks for the videos, 73 de G0IFI
There's a few restrictive factors here now I'm taking a close look at this experiment.
No.1 is the small width of the cut in the ground plane between the circuit and the part of the copper forming the antenna section on the board.
This will negatively impact the performance as there is going to be significant capacitance between the gate and ground at the input of the JFET. The MPF102 also has a little higher gate capacitance than the J310. This all contributes to act as a capacitive divider for the very short antenna terminating the extremely high gate input impedance of the FET... a few pF really matters here when we're dealing with megohms!
The use of a 2N2219 is also a handicap as it will not be anywhere near as 'hot' as a 2N5109 in terms of its RF performance.
I have a lot of 2N5109 as well as 2N4416A JFETs (perhaps lower gate capacitance than the J310) and this weekend I'm going to investigate this circuit myself and seek to squeeze every last ounce of potential out of it.
I plan to take it, as well as my homemade active loop antenna to a local park with no powerlines for hundreds of meters and make performance comparisons
Clever tip on using the loop tuner in conjunction with the adjacent mini whip. Induction and capacitance can produce interesting results with some radios. I'll try that on mine.
Thank you for posting this video. I have struggled with an active mini whip ~25 feet off the ground. The noise is terrible and antenna unusable. I have the RA0SMS version of the PA0RDT - it produces 10 KHZ 'spikes' across the entire HF band.
I never thought about attaching it to a stick and moving it around the back yard - brilliant. What a simple task that I completely overlooked.
I'll give your process a shot today to see if I can get a usable signal. As it is, @ 25 feet in the air with no obstructions, it is simply not usable.
Great video and I have been building and experimenting with the mini-whip myself. What I do miss in the video is the earth connection. If you want to get it in the clear then I found you need to bring the earth connection to the mini-whip. This shows in your video when you hold the whip close to the ground. Mounted on a 12 meter fiberglass pole with a separate earth going up to the whip I had excellent results.
Just moved into a flat where wire antennas aren't possible. I built one of these exactly as per the original circuit by RDT and it's astonishing. I think yours shows a better S/N ratio near the ground because you're giving its "earthy" side a capacitive coupling to ground. I ran a wire from the braid at the feedpoint of mine, connecting it to a water pipe and the noise dropped by 6 s-points. I'm going to ask the landlord nicely if I can get the thing mounted up on the roof, 4 stories up. Should be interesting. It's remarkable just how much signal this simple little thing does pull in. Thanks for another interesting video. 73
Sounds very interesting, how did it work out?
IIRC on this circuit it's really a matter of having it grounded to earth since that gives it a better amount of potential difference between the patch which is connected to the JFET and the feed line. I know that i've played with a version of a whip amp from Charles Wenzel which had similar characteristics where if I touched a wire attached to circuit ground the signals would peak and the noise levels would dramatically reduce on my SDR software. All this was with battery power as you did. I'm not an electrical engineer or a physicist but I think having any kind of ground improves the amplifier (even just some coiled up coax attached to circuit ground produces similar results in my own tests).
Dead right.
Hi.Peter. It looks to me like the sort of receive "antenna buffer" that would work best with a telescopic whip of around 60cm. You could slide it in then to note the results with different lengths. The comments about grounding seem valid too. Mounting it on top of an aluminum tube which is connected to the RF ground of the PCB will probably much improve performance, especially if the tube is then grounded also. It probably would be a great general purpose monitoring antenna, although for MF (and even for HF) my preferences are towards tuned loops fed into a differential antenna amplifier converting the high loop impedance down to one suitable for feeding the RX
I'm experimenting with a mini whip designed to be lower, compensating for the lower signal level that comes with a smaller distance between points within the electric field (V=E*d and whatnot) by a third transistor stage in the middle designed for voltage gain
Wow thanks Peter. You really are the home construction guru! Keep it up.
thank you for sharing your experience with us. Very interesting.
Thanks for this video Peter, it inspired me to do something similar with a Ramsey Electronics SA7 preamp kit although I had good results at 5m above the ground and with the outer coaxial cable shield uncoupled.
I just need to progress to the DC injection stage instead of using a 9v battery :)
I have built mine, but I am still using 9 volts 200 mA and when I tried to use 12 volts 200 mA the 2N4124 was becoming warm. What's the proper voltage and current, and how do I get that type of power source?
Sorry to hear that, but don't give up. Get a good earth connection, place it far away from objects outdoors and use the attenuator on your rig if needed. I did hear a lot more with this whip than with a 20 meter vertical.
To function, the PA0RDT MiniWhip Antenna *needs* proper Grounding.. Without (really) Grounding it, this Antenna-Type is almost useless. So it is not the best "portable"-Antenna. However, using it the Way, it is used in this Video, the Antenna seems to be a good Indicator for what would be a good Ground and what would be not.. :/
I say VK3YE, did you also test the antenna keeping it vertical? 73 de VU2UT.
Does it need to be? What is the pickup pattern like?
Is that an active loop? Very interesting when you placed inside the loop. Greetings from Argentina. 73
How come that "brick walls are very, very noisy"??
should you not have it well grounded not just floating ??
You are definitely right about that. Grounding the braid of the coax kills most of the background noise. He isn't giving the antenna a chance floating it like that.
Ohh dear! that antenna should be grounded in order for it to work properly! When its installed properly its capable of receiving the Russian Alpha signals at 12khz and many submarine comms transmitters from around the world from Melbourne
Hey mate, check this out.
Seems the Australian Government department of defense thought that the miniwhip concept was worthy of consideration, although theirs is conceivably more detailed and involved.
I found it interesting though.
No free lunch, earth it well 😉
DST-Group-TR-3522.pdf
@@Dazzwidd Its a great antenna if installed properly and keeping in mind that it works better on the lower frequencies.
vk3ye Peter, my understanding is that these antennas work best with a suitable groundplane and a good example of it use is : websdr.ewi.utwente.nl:8901/ where he says "Such an antenna only works well with a good grounding; ours is on top of a 20m high building, the upper part of which is all metal."
I think that some noise canceler (x-phase) will be much better :)
Yes
Hello, there have been changes to the Miniwhip now, here are my finding and experiments!
ua-cam.com/play/PLlsk-RUtmVpkul25Ye7UnvXMEvlryWrs4.html
An slightly alternative design is the one from PA0NHC (members.ziggo.nl/nvrecording/nhc/Projects/Miniwhip/20121025miniwhip.htm). Is less susceptible to IM and produces a slightly more moderate signal output.
PA0NHC has optimised the design.
A very poor test of a mini whip. what grounding arrangements did you have? Try a Chinese unit and get it up high in a quiet area. It outperforms amplified lops when built and used correctly, not waved around randomly[
you need to cover it with a pvc pipe so that it won't get wet when it rains outside XD