Messages

166

Equipment / Re: MLA-30 Loop antenna

« on: January 18, 2023, 1712 UTC »

From one of my posts in the MW thread....

Lowered voltage at the bias tee I was using to feed the MLA-30 preamp down to 4.5v last night. Add some voltage drop due to 75' of RG-6 feedline. Gain barely dropped at lower-HF bands and MW, while SNR likely improved. I still need to check voltage versus gain on upper-HF bands.

Positive supply voltage for the TL592B differential amp is listed at 3v to 8v. That tracks with my results. Gain at 3v (minus line loss) dropped considerably. The preamp at 1.5v dropped out.

12vDC as supplied by the stock USB->12vDC boost regulator in the bundled bias tee is likely overdriving the amp IC and potentially affecting SNR. YMMV, of course.

Dropping voltage might improve SNR with the inexpensive video preamp IC used in the MLA-30 design. I assume the MLA-30+ uses the same or similar chip.

Rob

Thanks for bringing up the suggestion for the lower supply voltage.

The reverse engineered schematics do not show any on board voltage regulator so I agree that  a +12v supply is too high, assuming the Chinese used a chip specified the same as the TL592B.  I've dropped the voltage into the bias Tee to +6vdc and the loop's amplifier gain seems the same. I'll try to make some signal strength measurements later this week.

Jim

167

Equipment / Re: MLA-30 Loop antenna

« on: January 10, 2023, 1916 UTC »

I bought a Chinese MLA-30+ and modified it a little. I desoldered most of the DC-DC converter in the bias T and ran in a line from a 12.6vdc linear supply. I tossed the thin stainless steel loop wire too. I took some aluminum jacketed 1/2" coax and made a loop. I squashed the jacket flat on each end, bent a 90 degree tab and drilled it. It seems to be about 2.9 uH

The antenna's output is run through a Navy surplus multicoupler that has a great 2 - 32 MHz preselector filter before the amplifiers.

Despite all of the MLA's engineering flaws in the amplifier design it performs fine mounted up high, outdoors when compared to an untuned 70' end fed wire. That leads me to believe a correctly designed active loop could perform even better.



The DW beacon

168

HF Beacons / Re: Teotwaki's Evening Beacon Log

« on: January 10, 2023, 0543 UTC »

2097.315 KHz    "A" beacon coming in great on the modified MLA-30+ loop antenna

169

SDR - Software Defined Radio / Re: kiwi software glitches or just problems at KFS?

« on: January 10, 2023, 0051 UTC »

After the latest storm hit California, both of the coastal SDRs, KFS and KPH appear to be offline. Anyone have any details?

January 5th Half Moon Bay Review

UPDATE: 4:25 p.m.: Power remained out in many parts of the Bay Area, much of the Midcoast, South Coast and Santa Cruz Mountains, after a long night punctuated by heavy downpours and howling winds.

On Thursday afternoon, PG&E said power could be restored to Moss Beach and Montara by 6:39 p.m. Hours later, the company extended its timeline and said it hoped to have power back on by 3 a.m. on Jan. 6. PG&E estimated it could return power to Pescadero by 11 p.m. There is still no timetable for Moss Beach and El Granada.

During a 1 p.m. press conference, PG&E Senior Vice President of Electric Operations Janisse Quinone said that 440,000 customers had lost power from the storm. Around 325,000 people had electricity restored by noon, with another 115,000 people still in the dark. She said PG&E is working to restore power to 40,000 people by the end of Thursday night, but because of hazardous road conditions and flooding, power could take longer than usual to restore. Customers can find and report outages at pge.com/outage.

170

HF Beacons / Re: Teotwaki's Morning Beacon Log

« on: January 06, 2023, 1443 UTC »

2097.320 KHz    "A" beacon, weak to barely audible
4095.700 KHz   DW. Fair signal.  BAT 12.7 oTMP 43 iTMP 48  PV 2
7039.300 KHz   Russian K beacon, fair signal

171

SDR - Software Defined Radio / Re: kiwi software glitches or just problems at KFS?

« on: January 06, 2023, 1436 UTC »

After the latest storm hit California, both of the coastal SDRs, KFS and KPH appear to be offline. Anyone have any details?

172

General Radio Discussion / Re: All right, fess up! :-)

« on: January 06, 2023, 0057 UTC »

Most anything the press reports on (especially anything technical) is wrong. This is a good example.

And how dare the public put up an antenna on public land without permission.

This cannot stand!           /s

173

General Radio Discussion / Re: All right, fess up! :-)

« on: January 05, 2023, 2138 UTC »

Fess up to the boneheads blabbing about crypto radio relay? 

 I can’t believe how much money was wasted on helicopters or forestry dummies hiking up steep slopes in the snow.

That video is going to end up giving a lot of hams some inspiration to go put up repeaters. Hopefully they wipe their fingerprints off.

174

HF Beacons / Re: The Desert Whooper

« on: January 02, 2023, 1826 UTC »

DW was hungry this morning! Around 9 AM I copied a couple of telemetry reports with voltage and current (PV) numbers over 2.2 Amps

175

HF Beacons / Re: Around 6140KHz there is a CW Beacon

« on: January 02, 2023, 1824 UTC »

Jim，

I use a old receiver 139B, http://www.crystalradio.cn/data/attachment/forum/202301/02/113513oewlwxxcmci6qw99.jpg

The antenna is 5 meters long wire.

That forum at  http://www.crystalradio.cn/ looks pretty interesting. I used Google to translate to English and look around a little.  That's an interesting radio too

176

HF Beacons / Re: Around 6140KHz there is a CW Beacon

« on: January 01, 2023, 1919 UTC »

Welcome to the forum WildDog! What are you using for a receiver and an antenna?

This signal on 6140 might actually be a legal utility beacon. I may move the message if it belongs in another sub-forum.

177

HF Beacons / Re: Coastal Slider Back On 4109.5

« on: January 01, 2023, 1755 UTC »

I caught CS turning on at 1752 Z

178

VHF/UHF Logs, including satellites and radiosondes / Re: Pirates 250.000-270

« on: December 27, 2022, 0219 UTC »

Right now on 253.85 I just have a single tone. Something less than a kHz

179

HF Beacons / Re: 4094 beacon

« on: December 27, 2022, 0213 UTC »

4094.13 is decent on the KPH SDR while the nearby DW whooper is banging in a S9 peak signal

180

HF Beacons / Re: Teotwaki's Morning Beacon Log

« on: December 23, 2022, 1455 UTC »

DW's signal has been coming up. Still has some mild but sharp fading but telemetry is easier to read

4095.700 KHz   DW. Fair signal.  BAT 12.8 oTMP 45 iTMP 51  PV 27