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Author Topic: Best MWDX antenna?  (Read 6093 times)

Offline pinto vortando

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Re: Best MWDX antenna?
« Reply #30 on: April 17, 2021, 1147 UTC »
The pigtail that came with my AN-200 is equipped with a 3.5mm stereo plug.  Plugging it into the AN-200 results in my reading continuity between tip and sleeve.
There is no continuity from the ring to either tip or sleeve.  Plugging in a mono plug also gives continuity tip to sleeve. 
To add to the possible confusion, the reviewer in the post #23 link called it a mono plug and the antique radio forum poster linked in post #27 opened up an AN-100, not an AN-200.
My AN-200 does not look like it can be easily taken apart without possibly destroying it so for now my guess is that the tip is the antenna connection.

Also, FWIW, be aware that the external antenna jack on portable radios can be mono, or in some cases, stereo.  The owner manual may not be very clear regarding which type.
You will have to make the proper determination for yourself.
« Last Edit: April 17, 2021, 1154 UTC by pinto vortando »
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Offline RobRich

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Re: Best MWDX antenna?
« Reply #31 on: April 17, 2021, 1339 UTC »
I use a mono cable to hookup the AN-200 if needed. An 1/8" connector to 1/8" connector for portables, or an 1/8" connector to RCA connector with the appropriate adapter for desktops. Not sure I bothered checking the hookup for continuity, but it works as expected, so.... :)

As pinto vortando noted, the AN-200 also works nicely for coupling other antennas for MW to portables. I have used it to couple my 148' LoG to various portables. The AN-200 loses directivity of course, but it still maintains enough circuit Q to continue working as a passive preselector.
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Offline alpard

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Re: Best MWDX antenna?
« Reply #32 on: April 17, 2021, 1519 UTC »
Managed to dig out my AN-200 from the attic.  I had a close peak on the 3.5mm input jack on the AN-200, and it says "Antenna Output".
This made me think that the pig tail 3.5mm connects to the input socket of the AN-200 which says "Antenna Output", and  could be connected to my R75 PL259 via adaptor.  It worked very poorly, and I threw it away to the attic for all that time.
« Last Edit: April 17, 2021, 1521 UTC by alpard »

Offline pinto vortando

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Re: Best MWDX antenna?
« Reply #33 on: April 17, 2021, 2151 UTC »
Managed to dig out my AN-200 from the attic.  I had a close peak on the 3.5mm input jack on the AN-200, and it says "Antenna Output".
This made me think that the pig tail 3.5mm connects to the input socket of the AN-200 which says "Antenna Output", and  could be connected to my R75 PL259 via adaptor.  It worked very poorly, and I threw it away to the attic for all that time.

The AN-200 probably won't do much for your R-75.  It is intended more to improve reception of a portable.
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Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #34 on: April 18, 2021, 0107 UTC »
Quote
pinto vortando - Plugging it into the AN-200 results in my reading continuity between tip and sleeve.
Thank you for that additional information. My surplus AN-200 was missing the cable and I found it odd that they would have used ring and sleeve. I did initially check all of the possible combinations with my LCR meter but could not determine which pins were active. It is possible that there is something wrong with my antenna. It did come from a surplus store after all.

As with yours, my AN-200 did not look like it could be easily dismantled without potentially damaging it.

As mentioned earlier in post #7, I subjected the NooElec Flamingo filters I purchased to some bench tests late this past afternoon. More to follow. I will post the results here on this thread.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #35 on: April 18, 2021, 0415 UTC »
I have used the AN-200 on my Kenwood R-2000 through the receiver's low-impedance input, though I used a variable gain preamp to handle the (huge?) mismatch. I only tend to do something like that if/when my outdoor antennas are disconnected, like during a storm, yet still wanting some radio nois... err, music or whatever in the background.

Suppose I could peak the AN-200 for an arbitrary MW frequency, then measure it with a VNA to get a better idea of its electrical characteristics. Maybe later tonight or tomorrow.
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Offline RobRich

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Re: Best MWDX antenna
« Reply #36 on: April 18, 2021, 0503 UTC »
I did a *very quick test* with a NanoVNA-H4. There was some measurement bounce due to stray capacitance, as in likely my proximity to the setup.

Peaked the AN-200 at 850KHz. Approximately 950-j245 with a SWR over 20:1; give or take maybe 5 to 10 percent. Even with the error margin, that means a considerable mismatch to a lower impedance input for an already negative gain antenna.

In the case of the AN-200, a standard 9:1 balun likely would help considerably if direct connecting to a low-impedance receiver input, such as the usual ~50-ohm jack. Around $15 on eBay, or wind ya' own. An alternative could be a low-noise preamp as I previously noted using with my Kenwood desktop.

BTW, some desktop receivers have high-impedance inputs, though those are often just paths through 4:1 transformers to the usual internal low-impedance circuit inputs. That 4:1 could help, though a 9:1 or slightly higher ratio connected to the low-impedance input might prove superior for signal transfer.

As for portables.... yeah, those 1/8" and similar small inputs can be all over the place. I would start with a 4:1 or 9:1, though perhaps even no transformer at all might suffice. Huge YMMV. Otherwise just capacitance couple the AN-200 to the portable's internal MW ferrite loopstick antenna. ;)
« Last Edit: April 18, 2021, 0509 UTC by RobRich »
Tampa, FL USA | US Map Grid EL88
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 + NE602 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
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Offline pinto vortando

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Re: Best MWDX antenna?
« Reply #37 on: April 18, 2021, 1611 UTC »
If the OP really wants to investigate which MWDX antenna would work best for him, my suggestion would be to visit the International Radio Club of America (IRCA) website and check out the free reprints available covering all types of MW antennas.  Another source would be the National Radio Club (NRC) Antenna Manuals volumes 1 through 3 as well as their Design and Theory manuals covering Loops, and Beverage and Longwires...  five books in all that along with the IRCA reprints should be more than enough to satisfy the MWDX enthusiast.
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Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #38 on: April 19, 2021, 0124 UTC »
As mentioned earlier in post #11, I inserted a NooElec Flamingo AM filter which I purchased to overcome the strong RF signals from AM transmitters near to my location. I purchased both the enclosed versions of a Flamingo AM and a Flamingo FM for evaluation. Both filters are well built and assembled. I performed some bench tests at specific frequencies to test their frequency response. Both filters performed as advertised by the manufacturer and I am pleased with them. Below you will find the filter response charts based on the tests that I performed using my HP/Agilent instruments.



Offline alpard

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Re: Best MWDX antenna?
« Reply #39 on: April 19, 2021, 0848 UTC »
They look excellent filters from the graphs. Thanks SIGINT.
I too sometimes suffer from overloading from an AM transmitter about 5 miles west of me.
So, if I point my loop to the West, then I get the strong AM signals from the transmitter all over the band popping up here and there everywhere.
This is a big problem.  So I have bought a set of Kiwa filters for MW and LW.  They are very old filters, and seem work OK.
Trouble is that now I do lots of listening for on MW DXing. When the MW stop filter is on, then the weak signals on MW gets blocked off.
So I must add some sort of switching to take out the filter when MW BCLing.  On SW BCLing, I need to switch on the MW blocking filter on.
I still hadn't add the switch, so ended up taking off the filter all together because SW condition is so poor, I hardly now listen to SW bands.
Just odd tuning around there, but mostly tune about MW bands for night time DXing. It has not been great either for DXing.
But I am still planning to add a 2 way switch for those filters.  The Kiwa filters are now out of production for some reason, but they are excellently built with heavy duty metal casings.

I wonder how you are using the filters and what your set up is. I guess it would depend on what bands you listen to most.

Offline alpard

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Re: Best MWDX antenna?
« Reply #40 on: April 19, 2021, 0851 UTC »
If the OP really wants to investigate which MWDX antenna would work best for him, my suggestion would be to visit the International Radio Club of America (IRCA) website and check out the free reprints available covering all types of MW antennas.  Another source would be the National Radio Club (NRC) Antenna Manuals volumes 1 through 3 as well as their Design and Theory manuals covering Loops, and Beverage and Longwires...  five books in all that along with the IRCA reprints should be more than enough to satisfy the MWDX enthusiast.

I feel they are all related and good to know even not directly related to the OP.  Initially I was curious what other MWDXers own and run for their DX antennas for the band, and what sort of DX signals they are hearing with them.
But I feel every idea and post is valuable for me for my learning the subject = MW DXing antennas

Offline NQC

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Re: Best MWDX antenna?
« Reply #41 on: April 20, 2021, 1556 UTC »
Hey All,

More  random comments :

Quite an interesting concept to think of a loop as a   "pre- selector".   Also ,a loop  certainly may not be a "substitute" for a serious outdoor wire antenna (of any type). A supposed rule of thumb ( not sure if exactly true or not ), If- a loop has ie, 100 ft of wire, even if well built,it  supposedly grabs only  1/10 of the energy of a well built  outdoor 100 ft long  antenna (comments ?). But Q and directional ability  are the advantages.

I have used both and REALLY liked having both at my disposal,way  back when. Unfortunately, any serious outside wire antenna is now out of the question for me .So it's loops or pretty much nothing.

 I suppose each  QTH is different re the type of noise encountered, operator's  "goals" , etc. One size (re anything) may not fit all.

Obviously one main   focus , IMHO, is Q .Not matter what you build, be it small tank ,loop or long wire or ground run. And at least in my experience with my (long gone) ultra high performance  DX crystal sets, the takeaway is  save every tiny bit of Q you can. It adds up.

Insulate and insulate again. Radio "loves" air- not solid surfaces. I even used to air  stand off ground runs until it reached rod. Maybe overkill to some, but Q bleeding seems to hide in some  unexpected places.

In my experience any  serious home brew tank/loop,etc,  starts with  the var cap. It is the first (and maybe the worst) place things can go wrong,IMHO .To me , nothing can replace a 500 pf 4 gang ceramic ( very important that it be ceramic )wired 2 gang as one leg, two gangs as the other. This will eliminate rotor loss. Such caps are often found in old signal generators. If purchased on line, they can be expensive. But WORTH it. I was cheap with mine and enclosed them in airy styrene boxes with  ceramic stand off  insulators  and quick solder  terminals. That way I can hard solder them into whatever project I feel like and not have to buy 12 of them (ha, ha).  6:1 (or better) Ball drives and shaft insulation  , panel  shielding, etc, are musts with theses caps. A definite "investment".

4 gang ceramic did well quite  even with solid copper  #20 cotton covered wire coated with poly. Such coils with bakelite var caps were noticeably down , even just by ear.4 gang ceramics with 660/46 litz are  simply stunning.

Back in the day, I took one of my 660/46  ferrite tank coils off the xtal set and coupled the long wire   to the Panasonic's ferrite.
With no ground wire on anything, the results were incredible. Station audio was pinched up really tight  and you would swear you were listening to a regen.The selectivity was   awesome. Using a ground knocked things down a lot.

 I guess any air  loop , tank , external ferrite bar coupler , etc are only as good as the components and insulation and the good practices/ techniques  used.

I gotta try another BIG Fe external coupler some time.I had SO much of this stuff before the "Great Purge" of 2019. I regret tossing  a fair amount of these  items (some of which which I MAY reacquire, maybe ) , but the   situation dictated it then .Oh well.

Also re air loops  used on 50 ohm receivers : I have always been a bit concerned (maybe unfounded) that it has loss written  on it (Unless you are talking Kiwa high dollar /50 ohm designed/  regen loops. I had a friend who had one.The performance would  blow you away).
 
I think it would have to be done right to (maybe) get it to work well . Just having a ratio'ed  secondary wound right on top of the tuned primary may not be so hot . My understanding , is that the pick up winding may also need to be  properly spaced away from the tuned primary as well as ratio'ed. On the AN -200 or a Select -a -Tenna with a jack, this isn't practical due to space  considerations . Just too big for a "grab and play" type of store bought antenna.

Even simply tapping an air  loop way down for 50 ohms may cause a (serious ?) Q reduction  re loading the loop ( comments ?). Admittedly, I have not tried this, so maybe I am not the guy to comment.

I'd  say  knowledge of RF physics is  at a "low  to moderate level " (at best) , so if I am off base on anything , I welcome correction for both myself and for the group to learn  from .

de NQC
« Last Edit: April 20, 2021, 1608 UTC by NQC »
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Offline RobRich

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Re: Best MWDX antenna?
« Reply #42 on: April 20, 2021, 1935 UTC »
The primary issues with the original inquiry are limited lot size, local RFI, and a nearby AM BCB.

If a rural location with plenty of space, I would say more like a phased beverage antenna system would be a good starting point for the OP.

Quote
Even simply tapping an air loop way down for 50 ohms may cause a (serious ?) Q reduction  re loading the loop ( comments ?).

Likely so assuming it was being done in the actual small airloop design, such as trying to get a coupling winding to present a ~50-ohm load, which probably is not happening anyway with these small airloop antennas anyway.

I suspect a transformer at the feedpoint (should?) be "okay enough" for our purposes. If a transformer at the feedpoint does significantly affect Q, then a low-noise preamp at the the feedpoint or even along the feedline to help overcome the match losses if needed could be used instead.
« Last Edit: April 20, 2021, 1939 UTC by RobRich »
Tampa, FL USA | US Map Grid EL88
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 + NE602 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
148' "Shielded" Loop-on-Ground | 18' End-Fed Vertical | 9' + 31' Verticals | 2x PA0NHC MiniWhips

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #43 on: April 21, 2021, 0036 UTC »
Quote
I wonder how you are using the filters and what your set up is. I guess it would depend on what bands you listen to most.

For now, I have only been testing the AM filter. My intent was to leave it in-line all the time as opposed to switching it in or out of the circuit. The theory behind that is to prevent receiver input overload, regardless of the band I am listening to. Input overload can produce what is called receiver de-sensing. De-sensing occurs because the IF AGC is reducing the input gain due to the presence of high level local signals and as a result reduced the receiver's sensitivity. I did a quick dirty test this morning and having the filter in or out of the circuit does affect receiver performance. With the AM filter out of circuit, the baseband noise floor was at -121dB. With the AM filter in-line, the baseband noise floor increased to -117.4dB. This means the receiver was admitting nearly 4dB more signal with the filter installed (pictures below).

So far, having the filter in-line has improved my AM band DXing. Without the filter the power house broadcast stations just hammer the IF AGC. With the filter the AGC attenuation level is lower and the receiver is admitting adjacent channels much cleaner. AM band DXing in my area is not all that interesting. Everyone carries the same boring syndicated sports or radio talk shows. Being on the border of Canada and the USA, I get syndicated junk from both sides. The real test will be when I go back and check my beacon list. Back in late February I logged 391 kHz, DDP, San Juan / Dorado / Luiz Munoz Marin Intl, Puerto Rico. That is nearly 2,000 miles away from my receiver location. Not bad for what is reported to be a 3kW NDB with a 200' vertical.

Nice find on the Kiwa filters. I had forgotten about those but I remember them being well regarded back in the days.




Offline RobRich

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Re: Best MWDX antenna?
« Reply #44 on: April 21, 2021, 0152 UTC »
My interest is HF, so I am more inclined to outright high pass MW BCBs with more extreme attenuation if absolutely required.

One of the best solutions I have right now is a PAR BCST-HPF 7th order elliptic high pass filter. Roll off below 160m is dramatic. Pair it with a preselector for even more dramatic results.

http://www.parelectronics.com/bcst-hpf-specs.php
https://www.eham.net/reviews/view-product?id=5086
« Last Edit: April 21, 2021, 0257 UTC by RobRich »
Tampa, FL USA | US Map Grid EL88
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 + NE602 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
148' "Shielded" Loop-on-Ground | 18' End-Fed Vertical | 9' + 31' Verticals | 2x PA0NHC MiniWhips