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Old 04-07-2012, 10:03   #1
tpreitzel
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Low Cost Wideband or Tunable Magnetic Loop Antennas

I'm still waiting for a lower cost, i.e. ~ $200, wide band magnetic loop antenna. AFAIK, at this time, 4 options exist for considerably MORE expensive magnetic loops:

1. Wellbrook's ALA-1530 (ships from UK)
2. Pixel Technologies' PRO 1B (ships from US)
3. MFJ Enterprises' MFJ-1786/1788 (ships from US)
4. AOR's LA-400 (ships worldwide)
Others even at $500?

Hopefully, the Chinese will pick-up this task of cranking out lower cost, but good quality wide band magnetic loops. ... I'm STILL waiting.

Last edited by tpreitzel : 23-07-2012 at 08:28.
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Old 04-07-2012, 11:59   #2
mvs sarma
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Quote:
Originally Posted by tpreitzel
I'm still waiting for a lower cost, i.e. ~ $250, wide band magnetic loop antenna. AFAIK, at this time, 3 options exist for considerably MORE expensive magnetic loops:

1. Wellbrook's ALA-1530 (ships from UK)
2. Pixel Technologies' PRO 1B (ships from US)
3. MFJ Enterprises' MFJ-1786/1788 (ships from US)

Others even at $500?

Hopefully, the Chinese will pick-up this task of cranking out lower cost, but good quality wide band magnetic loops. ... I'm STILL waiting.


can you try instead the PA0RDT active mini patch antenna? herer we can adopt a 500cm size rod antenna instead of patch like telescopic.

i used one for quite long lime and it works well. i dont say it gives voltage gain, but it provides enough current gain
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Old 04-07-2012, 16:12   #3
ianf
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This is a subject I'm interested in, I use the Degen MS31, or a long wire, the Degen quite good
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Old 04-07-2012, 17:31   #4
tpreitzel
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Quote:
Originally Posted by mvs sarma
can you try instead the PA0RDT active mini patch antenna? herer we can adopt a 500cm size rod antenna instead of patch like telescopic.

i used one for quite long lime and it works well. i dont say it gives voltage gain, but it provides enough current gain

Unfortunately, I don't have the time, tools, nor territory to build equipment. Even my brief alterations to Degen's 1103 were too time consuming. Unless someone has Roelof's design implemented in hardware for SALE, I'll have to settle for something else.
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Old 06-07-2012, 07:53   #5
tpreitzel
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Has anyone tried PK's loop antennas?

www.amradioantennas.com

I'm specifically looking at their A-Loop-SW620 for ~ $155 USD without shipping...

Last edited by tpreitzel : 06-07-2012 at 07:56.
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Old 08-07-2012, 05:51   #6
tpreitzel
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Although not a loop in the sense of my original post, readers in the USA might find this alternative antenna workable for receivers like Newstar's DR111. One can buy this unit assembled at the factory with a ferrite coiled with 70 turns for the AM broadcast band. One would only have to recoil the ferrite using 7 turns instead of 70 to allow a tunable frequency range ~ 5.5 MHz to 19 MHz which should work very nicely with most DRM broadcasts. Naturally, one could use more turns for working lower frequencies on the SM100 since this unit also allows for the use of an external antenna, e.g. a long wire for upper frequencies. Personally, the frequency range from 5.5 MHz to 19 Mhz is nearly perfect for my needs. One could also buy Ramsey's Signal Magnet in the form of a kit as well. Amazon sells both Ramsey's kit and pre-assembled versions so check CAREFULLY before buying.

Assembled for AM Broadcast band, not SW:

http://www.amazon.com/Ramsey-SM100WT...pd_sim_sbs_e_7

Kit:

http://www.amazon.com/Ramsey-SM100-S...d_rhf_dp_p_t_1

Last edited by tpreitzel : 08-07-2012 at 06:45.
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Old 11-07-2012, 13:46   #7
ianf
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I have ordered a PK Loop, the same model, I will report back
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Old 12-07-2012, 11:46   #8
Mikey
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Quote:
Originally Posted by tpreitzel
Has anyone tried PK's loop antennas?

www.amradioantennas.com

I'm specifically looking at their A-Loop-SW620 for ~ $155 USD without shipping...

Yes I bought one a couple of years ago. On 6 MHz it is ok but not spectacular when compared with something like a Sony AN LP 1. However on AM even here you will usually find that it filters out noise very effectively.As you go higher up the spectrum performance does improve very noticeably on AM. On DRM all I can say is that when using my NEWSTAR DR111 on every frequency including 49 meter band it usually adds at least one bar to the SNR/Signal Strength meter when compared to all of my other active antennas. One thing I would flag up this that although a 9 volt battery works ok, if you increase power to 12v or above it will extend the coverage of the antenna. At 9volts on mine performance drops off part way through the 16 meter band. Up the voltage to 12 or 15 volts and coverage goes to 18 MHz and beyond

Their MW land LW loops are also very effective though more expensive than the Chinese Alternative. The medium wave loop is literally twice the price of the TECSUN. But I still maintain that the improved performance makes it worth every penny.
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Old 12-07-2012, 16:07   #9
ianf
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Mikey thanks for this its very useful
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Old 12-07-2012, 20:08   #10
tpreitzel
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Well, if DRM is ever going to be acceptable to the masses, we'll need cheaper, i.e. less than $200, antennas which are compact in size and reject noise. Random wire antennas are generally too unwieldy to deploy and magnets for noise. We're all looking forward to Ian's experience with the PK loop and thank Mikey for his insight on its utility. I'll be conscripting some local labor to assemble Ramsey's SM100 kit so I'll also relate how it performs in the near future.

Last edited by tpreitzel : 12-07-2012 at 20:12.
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Old 20-07-2012, 09:44   #11
tpreitzel
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We've received and assembled the kit. If you don't have much free time like me, you can always recruit some help. Younger eyes are especially helpful for reading the ULTRA tiny text on diodes, etc. Even a magnifying glass would be helpful. Furthermore, learning proper soldering technique is a useful skill for the kids.

The only really messy part involved wrapping the shield with aluminum foil. It's doable, but expect to create a minor mess.

The kit went together flawlessly and works as advertised. We wound 7 turns on the ferrite for a frequency response from ~ 5.5 MHz to 19 MHz. After calibration, this range is very, very close to reality.

As far as performance, the SM-100 performs similarly to a ~ 32' random wire at night. When using Newstar's DR111 at night, one might even notice a slight reduction in the SNR when using the SM-100 versus the random wire. I'm assuming that the slight reduction in SNR is due to a reduction in noise. However, the quality of the signal is noticeably improved.

I noticed a slight reduction in sensitivity when using Newstar's DR111 with the SM-100 versus a random wire from frequencies from ~ 15 MHz to ~ 19 MHz which I'm assuming MIGHT be due to using 25' of RG-174 feed instead of RG-6. Note that Ramsey specifies a maximum frequency of ~ 15 Mhz for the SM-100 so I'm unsure if this slight reduction in sensitivity in the upper frequencies is due to design or my use of RG-174.

During the day, the SM-100 performs best when noise levels are higher. During the day, a user will POSSIBLY see a gain in SNR of ~ .5 bar when using Newstar's DR111 with the SM-100 versus a random wire. This improvement can mean the difference between achieving MSC lock or not during daylight hours. Although the improvement is NOT dramatic, it is noticeable.

For ~ $100, Ramsey's SM-100 is currently the best value in an amplified antenna as far as I know. I'd buy the SM-100 again in a heartbeat and it's easily superior to MFJ;s 1020C.

Although imperfect, Ramsey has a solid product in the SM-100.

Last edited by tpreitzel : 20-07-2012 at 09:48.
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Old 20-07-2012, 17:19   #12
tpreitzel
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Addendum on Ramsey's SM-100:

Although I'm unsure if it's related to some apparent improvement, I repositioned the tube holding SM-100's ferrite coil horizontally so the .2" slit in the aluminum foil faces the sky's zenith. I can honestly state that the improvement in signal quality CAN be dramatically improved during daylight hours under certain conditions. YMMV

Note: This unit amplifies the signal so I have no idea if it will damage Newstar's DR111. Use it at your own risk. Just avoid tuning the SM-100 to signals registering greater than 2 bars on Newstar's DR111. Use either the whip or external antenna for strong signals.

Last edited by tpreitzel : 23-07-2012 at 08:24.
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Old 23-07-2012, 08:27   #13
tpreitzel
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AOR LA-400

Although certainly not cheap and relevant to this thread as a lower cost alternative, it's a nearly IDEAL * design for a compact, low noise antenna for SWL. AOR finally got it right with the LA-400. The remote feature of the new LA-400 is very nice. Now, if someone in China could just produce a good quality product with similar capability at HALF the price of the LA-400.

* Drop the minimum operating temperature to -15 degrees centigrade or 5 degrees fahrenheit.

Last edited by tpreitzel : 23-07-2012 at 10:21.
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Old 01-08-2012, 22:09   #14
ianf
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Got my PK loops aerial up and running, seems better than the Degen on Air India Radio 9950kHz, peak is wider, easier to tune, will report on more as I use it.
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Old 01-08-2012, 22:24   #15
tpreitzel
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Quote:
Originally Posted by ianf
Got my PK loops aerial up and running, seems better than the Degen on Air India Radio 9950kHz, peak is wider, easier to tune, will report on more as I use it.

Great, Ian. I'm looking forward to your more detailed analysis.
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