Best MWDX antenna?

[~SIGINT~]

Rob,

Thanks for the prop link. I didn't have that one in my collection.

Same for Nooelec pre-amp. I'll put it on the list of items to order. I can sympathize with the use of the 10dB attenuator. I had the same issue with my Wellbrook loop. That is why I replaced my 10dB step attenuator with the Flamingo filters. They are now in-line all the time to attenuate the AM and FM bands by +/- 30dB.

[RobRich]

Welcome. I find the estimated values to often be close enough for casual skimming. I might fair 1-2MHz above the estimate if referencing broadcast SWL stations running substantial power and/or directional arrays.

Thankfully I do not deal with much overload here. The stations I mentioned are a couple of my worst offenders in the HF spectrum, and especially with me being right in the path of Radio Marti beaming into Cuba. I would not be surprised if Radio Rebelde is more like transmitter splatter and harmonics, either. The audio is often so compressed to have practically no dynamics and headroom left. I can almost imagine the final stage tubes singing and echoing along now. o.0


Now there is an area in Canada with an estimated MUF of 1MHz. Outlier perhaps, as I am not seeing any related space weather reports. Hmmm.

[RobRich]

Looking over my recent loggings in the shortwave section, I think my 31' vertical is back to working okay.

I *might* change out its ground radials if/when cooler weather arrives. Right now there are sixteen ~31' radials on the ground, but they are built with like "18-gauge" CCA speaker wire. The CCA seems to have held up to quick visual checks so far, but I have not run actual conductivity checks. I would prefer copper THHN or similar.

An alternative idea would be raising the vertical and using a couple or so elevated radials, though I am concerned it might have to be guyed unless I want to drop it each time a tropical weather system arrives.

[~SIGINT~]

I am trying to correlate the figures / prediction from https://prop.kc2g.com/ and it is not working for me right now. Based on the variety of other propagation tools that I use it seems skewed.

Here are the screen shots from the site compared to Collins PropMan, HamCap and VOACAP. All 3 of these track pretty close on a point-to-point circuit between Toronto and Boulder. I tweak these for worst case scenario, 100 Watts and 0dB gain on a dipole @ 35 feet off the ground. Even with that, the FOT does not come close to what I see on the website. The MUF seems pretty close. Something to further look into on a rainy day.

[RobRich]

About all I use it to do is for a quick check of MUF. Basically to get an idea of what the bands are going to look like for the next hour or few.

[RobRich]

MW is thus far active tonight. I should have adjusted the waterfall contrast, but anyway, ya' should get the point. Antenna is one of my active miniwhips.

[~SIGINT~]

I live in an RF rich area. Here is the spectrum from the end-fed longwire antenna plus the in-line 35 dB Flamingo AM notch filter.

[RobRich]

Playing around with the Airspy HF+ SDR setup tonight since I am in the den away from my usual radios.

I already had a KD9SV SV-CMC choke just upstream of my bias tee, plus some snap-on chokes at the mast base of the active minwhip antenna. I just added six turns of RG-316 on a Fair-Rite likely mix 31 or 43 snap-on choke between the bias tee and SDR. I did not measure actual numbers, as the noise floor was already decent IMO, but the waterfall looks a little cleaner in quick skim.

I suspect it was slight noise from the bias tee, as it is powered currently by a wall-wart. The wall-wart is a linear transformer, but it probably could use extra filtering. I have bias tees to which I added filtering caps, but I think this one is still stock.

I might change the bias tee for a filtered one and go back to a regulated linear PSU later tonight. I was trying to clean up some of the clutter by ditching the bigger PSU, but I suppose "oh well."


Went ahead with the components swap to a bias tee with filter caps and a regulated linear 13.8v PSU. Probably not much difference, at least regarding the HF noise floor, but ideally it should be the technically "better" configuration. Anyway.

[~SIGINT~]

I have been running an HP 6216A power supply instead of wall warts. The 6216A or the 6215A series are nice compact, lightweight units and are reasonably priced on eBay. They are also dirt simple to repair should they ever require any service. Nice old fashion transformer power supply design with ordinary components.

[RobRich]

I would not mind an used programmable lab power supply, but shipping for the heavy units usually ends up being quite expensive, plus assuming a seller even bothers to actually check it beyond a power-on test. o.0

Like when I once scored a new Eaton 5PX 1500 UPS on eBay for under $50 with free pickup from an area electronics recycler. It was an ~$1000 UPS, but I suspect few people bid due to how shipping costs were calculated and listed in the auction.

[~SIGINT~]

Hi Rob,

The 6216A measures all but 8" x 6" (and that 8" including extrusion for the knobs and the heat sink). It is a very small compact power supply which is why it is handy.

Below is a picture of my spare one. A friend who owns a surplus store gave it to me as it got dropped and smashed. I was hoping to find a junker somewhere and use it for the case but have not had any luck with that. I will probably eventually just get a plastic box and drop it in there.

[RobRich]

Yeah, I ageee the smaller HP Aligent supplies are good options, especially for the price compared to their larger siblings.

I have various power supplies, but I still would not mind a programmable lab supply like one of the Amrel units from years ago. However one of my concerns is getting a supply with a failed unobtanium part.

An example:

http://www.kerrywong.com/2015/05/06/amrel-pps-2322-programmable-power-supply-teardown/

[~SIGINT~]

I have an Agilent 66309D, a E3615A and a 3644A in the shop. You can see the 66309D and the E3615A at the bottom of my rack. I will be swapping the E3615A for the 3644A at some point. All are programmable, mind you, not via numerical keypad, but twirling the knob doesn’t bother me. All 3 are nice power supplies. E3615As are reasonably priced on the surplus market.

[RobRich]

Ya' had to go there. :p I do not even have a home office anymore. I think about doing a radio room or area of sort, but then I think about how often I would actually use it.

[RobRich]

Think one or both of my active miniwhips might have been damaged in a recent thunderstorm. Need to check the antennas and power supplies further. Yay?

I have like 2-3 amplified antennas collecting dust in parts storage as possible replacements if needed, but I am debating about even bothering with them. I mostly use my 31' vertical for casual MW/HF listening anyway.

It is about time to take a closer look at the existing antenna farm, too. I would like to update feedlines, deploy more and better radials for my ground-mounted verticals, etc.