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Author Topic: Active Antenna question  (Read 1750 times)
N4MU
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Posts: 235




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« on: April 20, 2019, 05:20:47 PM »

What's the best active antenna you know for under $100? Prefer to buy stateside if possible. I'm new to this aspect so please let me know the "why" it's the best. I'll be using it with a Tecsun 880 for casual amateur and shortwave listening. Thanks! Huh
« Last Edit: April 20, 2019, 05:22:58 PM by N4MU » Logged
KA3JJZ
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Posts: 26




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« Reply #1 on: April 20, 2019, 08:03:17 PM »

E Field actives are simply too prone to noise issues, and if they're poorly designed you will have more issues with overloading and noise than you know what to do with. You could find schematics on the web (search for the PA0RDT, which as I understand it, has gone some design revisions to improve its performance). You would want to put this as far away from the home as you can.

Of course you  could find a Sony AN100 on eBay but that's a rather poor alternative. You can do better.

W6LVP has been selling active loops (and added a loop kit, similar to the Wellbrook model) for some time now and is a top performer on eHam reviews. The loop kit would run a bit more than your limit, but the advantage being that you get support from Larry that you likely won't get elsewhere.

Many many satisfied customers - I think it's worth checking out...here is the website

https://www.w6lvp.com/

Mike
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AB4KA
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Posts: 7




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« Reply #2 on: April 21, 2019, 11:24:40 AM »

http://www.mfjenterprises.com/Product.php?productid=MFJ-1020C

A lot of folks aren't fans of MFJ products, but generally I've had good service from them.

When it comes to shortwave I tend to go with the old school of thought...get as much wire as high in the air as you can.  One of the best working antennas I've ever had was a loop of wire running out of my window and under the eaves of the house.
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KA3JJZ
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Posts: 26




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« Reply #3 on: April 21, 2019, 07:37:20 PM »

The problems with indoor antennas - even the MFJ one - would be noise. You will pick up a good amount from just about any noisy appliance in the vicinity. A loop, on the other hand, is more resistant to E field noise

There is yet another alternative, and I built one of these when I lived on the top floor of a 3 story condo that had a huge attic.  Worked quite well for what it was. I was using a TenTec RX320, Drake R7A and Yaesu FRG7, and it worked well with all 3...if you are stuck with something indoors, this can be built on the cheap

http://www.hard-core-dx.com/nordicdx/antenna/hidden/carploop.html

Mike
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G4AON
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Posts: 1378




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« Reply #4 on: April 25, 2019, 01:39:37 PM »

Active antennas are easy and cheap to make. There is nothing special about the commercial or eBay units. I have a homebrew PA0RDT in the corner of the garden, I use it with a QS1R SDR to feed CW Skimmer spots to my log and to the Reverse Beacon Network. The performance is excellent and it’s only 7 feet above ground.

A friend uses a Wellbrook loop fed via the same interface that my antenna uses and reports it as being less prone to noise pickup than the original interface.

https://www.qsl.net/g4aon/pa0rdt_aa/

73 Dave
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N4MU
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Posts: 235




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« Reply #5 on: April 27, 2019, 05:32:02 AM »

To all: Thanks for the info. I have my work cut out for me for the "summer doldrums" project. I will visit all links and see what moves me. LOL I can have a reasonable outdoor antenna and want to be able to just sit and tune/listen on the patio...connected to the outside antenna. I live fulltime in a RV so it should be interesting. Have had great success with my ham rig and a Tarheel antenna so maybe there's hope. Thanks again and I appreciate everyone's suggestions.
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KD7RDZI2
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Posts: 425




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« Reply #6 on: April 28, 2019, 08:36:15 AM »

In addition to the g4aon/pa0rdt antenna, you may have a look to the dirt cheap "Degen 31MS MW/SW active loop antenna", which covers most of the HF. Contrary to many other active antennas this antenna being a tuned loop is very selective. In practice you will likely never overload the receiver. It's like having a preselector at the antenna. It's for portable use when it doesn't rain.
« Last Edit: April 28, 2019, 08:39:19 AM by KD7RDZI2 » Logged
VA3VF
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Posts: 2861




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« Reply #7 on: May 02, 2019, 09:51:58 AM »

Quote
In addition to the g4aon/pa0rdt antenna, you may have a look to the dirt cheap "Degen 31MS MW/SW active loop antenna", which covers most of the HF.
I second that. I don't have the combined MW/SW, as I purchased the MW only and then the SW only versions, before the combined model was released.

Don't expect an earth shattering performance, but for the price - the lowest priced active antenna I know of - it's a winner.

That said, I use a mini-whip most of the time. I feed it with a much lower voltage though. At 12V, performance leaves a lot to be desired.
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VA3VF
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Posts: 2861




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« Reply #8 on: June 04, 2019, 09:21:33 AM »

That said, I use a mini-whip most of the time. I feed it with a much lower voltage though. At 12V, performance leaves a lot to be desired.
An update on the Mini-Whip input voltage.

The Mini-Whip is usually spec'ed to work with an input of 12-15 V. I don't know if the different Mini-Whip builds vary, but the one I use does not work well with 12 V, lots of IMD.

I have been reducing the voltage as I come across quality AC adapters with the right polarity. I know, I could simply have re-wired the barrel connector if the polarity was not the correct one. Roll Eyes

This week I found a good AC adapter with an output of 5 V. Tried it yesterday, and the results are excellent. So, if your Mini-Whip is not giving you quality results, try reducing the input voltage.

As a side note,  I had also added the recommended ground wire some time ago. In my particular installation, no difference was noticed.
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HFCRUSR
Member

Posts: 350




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« Reply #9 on: June 05, 2019, 09:49:36 AM »

That said, I use a mini-whip most of the time. I feed it with a much lower voltage though. At 12V, performance leaves a lot to be desired.
An update on the Mini-Whip input voltage.

The Mini-Whip is usually spec'ed to work with an input of 12-15 V. I don't know if the different Mini-Whip builds vary, but the one I use does not work well with 12 V, lots of IMD.

I have been reducing the voltage as I come across quality AC adapters with the right polarity. I know, I could simply have re-wired the barrel connector if the polarity was not the correct one. Roll Eyes

This week I found a good AC adapter with an output of 5 V. Tried it yesterday, and the results are excellent. So, if your Mini-Whip is not giving you quality results, try reducing the input voltage.

As a side note,  I had also added the recommended ground wire some time ago. In my particular installation, no difference was noticed.
I've been contemplating this reduced voltage thing for a while. I have a Wellbrook loop antenna and I actually called Andy out there in the UK for consult on this. He told me I could not use less than 12V or the loop wouldn't operate as designed. So I never tried it but I think I might anyway for experimental purposes-do you think it'd be OK as in not damaging components?
I tested the wallwart he sent with the loop and it surprisingly is a steady 12V exactly, unlike most wallwarts that tend to run higher than stated.
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Not a ham, but an avid hobbyist in HF world. All things, short of transmit happen in this shack.
VA3VF
Member

Posts: 2861




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« Reply #10 on: June 05, 2019, 10:30:24 AM »

I think I might anyway for experimental purposes-do you think it'd be OK as in not damaging components?
Wellbrook, ie. Andy, has a very good reputation for quality and performance. In this case, I would not second guess the designer.

I have never seen a circuit diagram of a Wellbrook device. If the device is properly regulated, a very likely thing, reducing the voltage to less than half its nominal value, as I did, will certainly not work. I do not think it'll damage the device, but if you try it, do it at your own risk and expense.

I tested the wallwart he sent with the loop and it surprisingly is a steady 12V exactly, unlike most wallwarts that tend to run higher than stated.
You did not mention if the wallwart is of a linear or switching type. A regulated linear adapter is almost impossible to find these days. An unregulated one can output a much higher voltage than the one listed, 30% higher is not unheard of. Linear wallwarts are 'clean' devices RF wise.

If your walwart is of the switching type, they are much more 'on the money', as far as output voltage is concerned. The problem with them is that the bad ones will send you to RFI 'hell'.

The good wallwart I mentioned in my post is of the switching type, and the reason I said it's a good one it's because I did not detect any RFI.
« Last Edit: June 05, 2019, 10:33:24 AM by VA3VF » Logged
HFCRUSR
Member

Posts: 350




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« Reply #11 on: June 05, 2019, 11:35:11 AM »

I think I might anyway for experimental purposes-do you think it'd be OK as in not damaging components?
Wellbrook, ie. Andy, has a very good reputation for quality and performance. In this case, I would not second guess the designer.

I have never seen a circuit diagram of a Wellbrook device. If the device is properly regulated, a very likely thing, reducing the voltage to less than half its nominal value, as I did, will certainly not work. I do not think it'll damage the device, but if you try it, do it at your own risk and expense.

I tested the wallwart he sent with the loop and it surprisingly is a steady 12V exactly, unlike most wallwarts that tend to run higher than stated.
You did not mention if the wallwart is of a linear or switching type. A regulated linear adapter is almost impossible to find these days. An unregulated one can output a much higher voltage than the one listed, 30% higher is not unheard of. Linear wallwarts are 'clean' devices RF wise.

If your walwart is of the switching type, they are much more 'on the money', as far as output voltage is concerned. The problem with them is that the bad ones will send you to RFI 'hell'.

The good wallwart I mentioned in my post is of the switching type, and the reason I said it's a good one it's because I did not detect any RFI.

Not sure how to tell if it's linear or switching-it simply says "class II transformer". I will leave it be though-it works very well at 12V I just thought maybe with less voltage I could maybe eliminate even more noise while maintaining desired signals.
Thanks for the quick response!
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Not a ham, but an avid hobbyist in HF world. All things, short of transmit happen in this shack.
VA3VF
Member

Posts: 2861




Ignore
« Reply #12 on: June 05, 2019, 01:56:45 PM »

I think I might anyway for experimental purposes-do you think it'd be OK as in not damaging components?
Wellbrook, ie. Andy, has a very good reputation for quality and performance. In this case, I would not second guess the designer.

I have never seen a circuit diagram of a Wellbrook device. If the device is properly regulated, a very likely thing, reducing the voltage to less than half its nominal value, as I did, will certainly not work. I do not think it'll damage the device, but if you try it, do it at your own risk and expense.

I tested the wallwart he sent with the loop and it surprisingly is a steady 12V exactly, unlike most wallwarts that tend to run higher than stated.
You did not mention if the wallwart is of a linear or switching type. A regulated linear adapter is almost impossible to find these days. An unregulated one can output a much higher voltage than the one listed, 30% higher is not unheard of. Linear wallwarts are 'clean' devices RF wise.

If your walwart is of the switching type, they are much more 'on the money', as far as output voltage is concerned. The problem with them is that the bad ones will send you to RFI 'hell'.

The good wallwart I mentioned in my post is of the switching type, and the reason I said it's a good one it's because I did not detect any RFI.

Not sure how to tell if it's linear or switching-it simply says "class II transformer". I will leave it be though-it works very well at 12V I just thought maybe with less voltage I could maybe eliminate even more noise while maintaining desired signals.
Thanks for the quick response!
If it says transformer and it's heavy, compared to other wallwarts, you likely have a linear regulated wallwart. Take good care of it, those are rare these days. Wink
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HFCRUSR
Member

Posts: 350




Ignore
« Reply #13 on: June 05, 2019, 04:29:07 PM »

I think I might anyway for experimental purposes-do you think it'd be OK as in not damaging components?
Wellbrook, ie. Andy, has a very good reputation for quality and performance. In this case, I would not second guess the designer.

I have never seen a circuit diagram of a Wellbrook device. If the device is properly regulated, a very likely thing, reducing the voltage to less than half its nominal value, as I did, will certainly not work. I do not think it'll damage the device, but if you try it, do it at your own risk and expense.

I tested the wallwart he sent with the loop and it surprisingly is a steady 12V exactly, unlike most wallwarts that tend to run higher than stated.
You did not mention if the wallwart is of a linear or switching type. A regulated linear adapter is almost impossible to find these days. An unregulated one can output a much higher voltage than the one listed, 30% higher is not unheard of. Linear wallwarts are 'clean' devices RF wise.

If your walwart is of the switching type, they are much more 'on the money', as far as output voltage is concerned. The problem with them is that the bad ones will send you to RFI 'hell'.

The good wallwart I mentioned in my post is of the switching type, and the reason I said it's a good one it's because I did not detect any RFI.

Not sure how to tell if it's linear or switching-it simply says "class II transformer". I will leave it be though-it works very well at 12V I just thought maybe with less voltage I could maybe eliminate even more noise while maintaining desired signals.
Thanks for the quick response!
If it says transformer and it's heavy, compared to other wallwarts, you likely have a linear regulated wallwart. Take good care of it, those are rare these days. Wink
I never gave it a thought before but hell yeah it's substantially heavier than my others here. And leave it to Andy to give the best. Thanks!
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Not a ham, but an avid hobbyist in HF world. All things, short of transmit happen in this shack.
VA3VF
Member

Posts: 2861




Ignore
« Reply #14 on: June 12, 2019, 08:05:29 PM »

That said, I use a mini-whip most of the time. I feed it with a much lower voltage though. At 12V, performance leaves a lot to be desired.
An update on the Mini-Whip input voltage.

The Mini-Whip is usually spec'ed to work with an input of 12-15 V. I don't know if the different Mini-Whip builds vary, but the one I use does not work well with 12 V, lots of IMD.

I have been reducing the voltage as I come across quality AC adapters with the right polarity. I know, I could simply have re-wired the barrel connector if the polarity was not the correct one. Roll Eyes

This week I found a good AC adapter with an output of 5 V. Tried it yesterday, and the results are excellent. So, if your Mini-Whip is not giving you quality results, try reducing the input voltage.

As a side note,  I had also added the recommended ground wire some time ago. In my particular installation, no difference was noticed.
An interesting coincidence. The new version of the Mini-Whip from the vendor I purchased mine, now says that it can be powered with 5-12 Volts.
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