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Author Topic: Best MWDX antenna?  (Read 49297 times)

Offline NQC

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Re: Best MWDX antenna?
« Reply #15 on: April 14, 2021, 1644 UTC »
Hey All.
Alpard: 20X20 M is a fairly big area and without getting overly specific, I feel that a lot could be done in that size space.

Just to try something different, a number of years ago, I had reading about low noise (wire) antennas for HF/B'cast.
These sometimes required multiple grounds , multiple chokes, etc, etc. I never built any because I couldn't meet the specs required.
So a search for "low noise antennas" may get you somewhere.Perhaps you can quickly find the "class" of common mode choking wire antennas that I refer to here.

What wave lengths you'd want to construct these- perhaps there are different schools of thought as to how long to make them and how to construct them. Long has it's  has good points
but in an overloaded big signal and/or big noise environment maybe big isn't so great either, even re dx. Q is the key and a circuit that uses more variable capacitance and less inductance at the desired wavelength could be given some consideration. Also short 3 wire 20 or 30 ft  flat top spaced at 3 ft between  wires .It's all bonded on feed line end and  all open / NOT bonded  at the far end.

Feed line Shielding or feed line spacing will probably apply.Again, just a class or two of home brew inexpensive antennas could be tried for grins. Maybe they are for you, maybe not.

Not sure what may be worst of your issues: Arc/ power line noise -or-  local "device noise ( plasma TV's  noisy power supplies, etc) -or -local  broadcasts or other strong RF from off far away.
So your mileage , options and interests may vary.

Not sure if you have played with medium sized air loops (with /or with out low Z coupling loop/coax fed) . Or air loop just coupled to ferrite.True, it is a VERY small antenna compared to large out door custom arrays. But they have some  very interesting properties  and I have found them a lot  of fun to play with IF built well.

K
Station main receiver : Bed springs to  blue razor blade detector to 2000 ohm cans to steam  radiator. Grid FN 42

Offline alpard

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Re: Best MWDX antenna?
« Reply #16 on: April 14, 2021, 1653 UTC »
I was going to cut the lead and connect it back with the polarity reversed of the other PSU I have,  if the ferrite filters on the original PSU didn't work.  But it did. :D

I was thinking that too.  Countryside open field or near the sea side location with clear and high open space would be best for Radio work with big and large antennas.
Otherwise, in the residential areas and for the small garden house dwellers, maybe smaller antennas such as Active Loops are more suited?
« Last Edit: April 15, 2021, 1931 UTC by alpard »
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Offline NQC

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Re: Best MWDX antenna?
« Reply #17 on: April 14, 2021, 1712 UTC »
Also all  sorts of  types of   counterpoise   and ground rods experiments-and- Shortish verticals with  evenly spaced out  loading coils  with  radials or screen  -or- rods or spaced out rods AS antenna-or-single rod AS antenna, etc, etc. ALL sorts of options re all different types antenna designs  and the  different types of noise being encountered,
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Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #18 on: April 14, 2021, 2348 UTC »
I concur with the APC Line-R. I use them exclusively although they are protecting the servers, network, PC, TV etc ... that do not require a UPS. My AC line filtering is exclusively accomplished with Topaz Ultra-Isolation Line Noise Suppressor Model 91001-31 transformers. They are generally well recognized in the broadcast, audio recording industry, medical applications and labs. Their common-mode noise rejection is 146 dB @ 100 kHz and normal-mode noise rejection is 65 dB @ 100 kHz. Efficiency is 95% typical. You want the ones with 0.0005 pF inter-winding capacitance. A cheaper alternative is to wire a Corcom (or equivalent) EMI filters backwards, I.E. the AC line connect to the load side of the filter and the line side of the filter connected to the radio. Most of these filter are designed to prevent equipment from leaking noise back into the power line so when you flip the filter around you are preventing AC line noise from leaking past and into the radio.

As for the modem, this is an interesting item to watch:
VDSL RFI Detection and how to report it to OFCOM https://www.youtube.com/watch?v=tpcWYoDEh7U

The software and information can be found here:
https://rsgb.org/main/technical/emc/vdsl-interference-reporting/

In a nut shell, you take an I/Q recording of suspected interference and you run it through the software for analysis. There are also sample I/Q files on the site that can be used for testing purposes.

Ok, now we are completely off topic but what the heck, 300+ views so I will take it as there is some interest in the tread.
« Last Edit: April 15, 2021, 0007 UTC by ~SIGINT~ »

Offline alpard

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Re: Best MWDX antenna?
« Reply #19 on: April 15, 2021, 1542 UTC »
Also all  sorts of  types of   counterpoise   and ground rods experiments-and- Shortish verticals with  evenly spaced out  loading coils  with  radials or screen  -or- rods or spaced out rods AS antenna-or-single rod AS antenna, etc, etc. ALL sorts of options re all different types antenna designs  and the  different types of noise being encountered,

I have a few redundant mobile whips for HF ham bands.  Could they be converted / modified to work for MW DX Rxing by adding loading coils and stuff. Not sure how efficient it would be for MW DXing though.
« Last Edit: April 15, 2021, 1545 UTC by alpard »
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Offline alpard

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Re: Best MWDX antenna?
« Reply #20 on: April 15, 2021, 1544 UTC »

In a nut shell, you take an I/Q recording of suspected interference and you run it through the software for analysis. There are also sample I/Q files on the site that can be used for testing purposes.

Ok, now we are completely off topic but what the heck, 300+ views so I will take it as there is some interest in the tread.

No probs.  They are all related to each other, and we are learning something about them. That's cool.
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Offline RobRich

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Re: Best MWDX antenna?
« Reply #21 on: April 15, 2021, 1856 UTC »
I like and use APC for UPSs, but my two old Opteron 32-core servers and various network equipment are on an Eaton 5PK 1500. I scored it for under $50 new in the box via eBay. ?! I suppose nobody wanted to pay the shipping cost. It was a local pickup for me. :)

----------------

If those are loaded HF whips, you might find a combination of load coils and one of the whip sections to end up near "resonance" at some exceedingly tiny slice of the MW band. The other issue will be efficiency, which could fall to a few or even a fraction of a percent as frequency decreases. Both are products of the wavelengths involved.

For example, if unloaded, you would need an ~139 meters to build a quarter-wave vertical and a decent ground radial field to be near resonance at 530KHz. o.0

----------------

If MW DX is a distinct interest, have you looked into building a serious ferrite rod loopstick antenna? Not just a single ferrite like in a portable radio, but up to several large ferrite rods stacked together. Also you would need litz wire for winding the coils, a suitable tuning capacitor, and probably a length of PVC pipe as an easy-to-assemble casing.

Another popular DIY project for AM reception, though less exotic and potentially less performant than a stacked ferrite loopstick, is the box loop antenna. All you need is 2-4 supports, some wire, and a variable capacitor.

Either can be made to be remote mounted, remote rotated, and even remote tuned if you want to spend the time, effort, and a little money building them.

----------------

On a side note, I am curious if you have tried any of the off-the-shelf airloop tuned MW antennas? I have a Tecsun AN-200. Costs about $35. I am not really into AM BCB radio, so I can not give a thorough review, but it does null and peak signals decently with my G3, PL-330, etc. radios assuming there is not highly intrusive RFI noise from a multitude of directions. Also, it is compact and light enough to take along with a good portable receiver to a hopefully more RFI quiet location, like maybe a local park or similar.
« Last Edit: April 15, 2021, 2240 UTC by RobRich »
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Offline East Troy Don

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Re: Best MWDX antenna?
« Reply #22 on: April 15, 2021, 2138 UTC »

On a side note, I am curious if you have tried any of the off-the-shelf airloop tuned MW antennas? I have a Tecsun AN-200. Costs about $35. I am not really into AM BCB radio, so I can not give a thorough review, but it does null and peak signals decently with my G3, PL-330, etc. radios assuming there is not highly intrusive RFI noise from a multitude of directions. Also, it is compact and light enough to take along with a good portable receiver to a hopefully more RFI quiet location, like maybe a local park or similar.

Ditto on the AN-200....wonderful bang for the buck !
Primary: Yaesu FRG-7700  Secondary: ICOM R75 Tertiary: Grundig  750. Tecsun PL-990X, Tecsun PL-880 . Malahit DSP SDR V3,  Alpha Delta  SWL Sloper antenna. : Also, 1940 Mantola am/sw tube. CountyComm GP-5/SSB hand held, Tecsun PL-380 ,et al.  QTH: EAST TROY WI  USA.  Sea Level: + 320 meters .  75 miles (but not far enough) NNW of Chicago

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #23 on: April 16, 2021, 0056 UTC »
3 for 3 for the Tecsun AN-200. I had seen this review https://youtu.be/F8Jlu2NuPWo and by shear luck I later found one sitting on the shelf at a local surplus dealer a couple of months ago. I took it home, gave it a nice cleaning and assembled a BNC adaptor to be able to connect it to a receiver. I cannot give an honest review at this time since I have not had much opportunity to play with it so far but it is a nice loop antenna.

Here are a couple of sites with an anatomy of the AN-200.
https://antiqueradios.com/forums/viewtopic.php?t=261183
https://www.qsl.net/lx2sm/html/tecsun_an-200_infos.html

Offline alpard

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Re: Best MWDX antenna?
« Reply #24 on: April 16, 2021, 1525 UTC »
I do have an AN-200.   I have not thought it can pull the MWDX signals from the other part of the world.
It was OK for pulling low powered AM stations from hundreds miles away right enough.
I used to use it a few months ago, but put it away somewhere. Will need to find it, and put it on again.

The other thing about AN-200 is that, it worked better  magnetic way.  It was great for portables, but
not very good for the desktops without ferrite core antennas.  It wasn't working great with my R75 when connected
via 3.5mm headphone jack, and then PL259 adaptor.

Would it work ok with SDRs?
What kind of DX signal can it hear?
« Last Edit: April 16, 2021, 1528 UTC by alpard »
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Offline RobRich

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Re: Best MWDX antenna?
« Reply #25 on: April 16, 2021, 1856 UTC »
The MW DX signals are going to be arriving via skywave propagation, so your best bet with the small AN-200 is being outside. A small airloop is about directivity and circuit Q, with the antenna tuning capacitor acting not only to peak signal transfer for your portable, but also to act as as a sharp passive preselector.

Grab a portable with known decent AM performance. Go outside at night, preferably when it is dark in both your and the desired DX area, and hopefully find a RFI quiet location. Having a small table for the radio and antenna can help; plastic or wood would be preferable to a potentially RF-conductive metal table.

Rotate the AN-200 to null local RFI and/or local AM stations, tune the antenna carefully to your radio's frequency, and start listening closely around the noise floor. *Headphones* can help. No guarantees, but you might be surprised, especially if you have been using the AN-200 inside a RFI-filled house like many usually do.
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Offline pinto vortando

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Re: Best MWDX antenna?
« Reply #26 on: April 16, 2021, 2305 UTC »
Another ditto on the AN-200, it can provide much performance enhancement of a portable.
Another use of the AN-200 is in its ability to inductively couple a "longwire" antenna to a portable.
Most portables rely on the internal loopstick for MW reception and do not provide a means for connecting
an external antenna (typically, the whip is used for SW and FM and the external antenna jack is for SW only).
Plug the wire antenna into the AN-200 via its 3.5mm jack and place the loop near the portable so as to
inductively couple the signal into the radio.  You will lose much of the directional capability of the loop but
you will gain the ability to use the wire antenna.

Regarding the MFJ 1026, it is worth every penny as it oftentimes in a noisy environment is the difference between
hearing a signal or just listening to the noise.  However, you will have to modify it for use on MW and below.
This involves removing the high pass filters on the main and aux inputs.
Das Radiobunker somewhere in Michigan

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Re: Best MWDX antenna?
« Reply #27 on: April 17, 2021, 0135 UTC »
Be careful of the AN-200's 3.5mm connection. At this link https://antiqueradios.com/forums/viewtopic.php?t=261183 you will find the author describing that "The 3.5mm female stereo jack that is used for the external antenna connector. Only the Ground and first ring are used on the male connector the tip is not connected to anything" This is the way I built my adaptor, ring and ground.

Offline alpard

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Re: Best MWDX antenna?
« Reply #28 on: April 17, 2021, 0820 UTC »
Great info and advice. Thanks.
Will try out with my AN-200 again with the ideas suggested here.

MFJ1026 was just too expensive for my budget.
 I was seriously thinking of getting the Chinese made QRM eliminator but it also seems cover from 1Mhz only,
not fully covering MW band. The price was good, I was offered 38 Euros from the seller for it
including delivery.
« Last Edit: April 17, 2021, 0952 UTC by alpard »
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Offline alpard

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Re: Best MWDX antenna?
« Reply #29 on: April 17, 2021, 0842 UTC »
Be careful of the AN-200's 3.5mm connection. At this link https://antiqueradios.com/forums/viewtopic.php?t=261183 you will find the author describing that "The 3.5mm female stereo jack that is used for the external antenna connector. Only the Ground and first ring are used on the male connector the tip is not connected to anything" This is the way I built my adaptor, ring and ground.

Indeed. I read "The 3.5mm female stereo jack that is used for the external antenna connector. Only the Ground and first ring are used on the male connector the tip is not connected to anything."

Also "
airrace48 wrote:
Do you think that I could connect the AN100 to my antenna terminal utilizing the connection point on the AN100 shown in your photo with the red arrow? What about my ground terminal?

It would probably not work very well with this radio as it looks like from the schematic that it works best with a long wire. You could try it, it probably would not hurt anything but the an-100 antenna is really meant to be electromagnetically coupled with a sets built in loop antenna."


This is a vital critical info on this antenna I take it.
« Last Edit: April 17, 2021, 0850 UTC by alpard »
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