Messages

1

Equipment / Re: NASA Marine Active Antenna for reception problems

« on: July 20, 2025, 1346 UTC »

Thanks for your reply.   The antenna is used with the Nasa Target HF-3, which is also from the same company.  At the back of the radio, it has red panel, which means that it has built-in amp for the NASA antenna.   When it is used with the built-in amp, the antenna seems to give more overloading at nights on the lower frequency reception below 7 Mhz.   Hence I use the battery powered T-Bias with around 10-11V DC input into the T-bias.

When the NASA antenna is not powered by T-Bias or built-in amp, it becomes totally deaf, and the reception goes silent.  The NASA antenna must be powered by the amp (either by the builtin amp or T-bias) at all times in order to get any reception on the radio.  Hope it makes sense.

2

Equipment / Re: Receiver Advice

« on: July 19, 2025, 2057 UTC »

It would depend on what type of listening you would be doing.  If you are only interested in listening to the nearby stations in your own country or your own continent with powerful output transmissions, then cheap portable radios will do the job.    No need to spend any more than $50 for sw radios in that case. 

However, if you are interested in listening to the weak signals from the other side of the globe with low power output AM stations (in my case South American, South Pacific, African stations .. etc), then those extra facilities, gadgets and devices  they provide in the high end receivers do help, and are must for DXing the weak signals.

My favorite receivers for the weak signal copying are, SDRPlay RSPdx, RSPdx-R2,  Elad FDM-Duo for SDRs, and from the old radios - NRD JRC-535, Kenwood R-5000, ICOM ICR-70.   Tecsun S-2200x is also a very good radio for DXing.

It is also very important to remind yourself, that your radio is only good as your antennas.  No radio will work properly without good antennas feeding the signals into them.

3

Equipment / NASA Marine Active Antenna for reception problems

« on: July 18, 2025, 1103 UTC »

I got this antenna a few days ago, and installed it.  It works great during the day above say 9 Mhz upwards.
But at nights, and below 7Mhz, it seems to be overloading the radios.  It is saturating the reception at nights with MW signals on HF.

What could be done to this antenna to improve the reception?  Add attenuator 10 - 20 dB?  Feed with less input voltage say 10V instead of 12V?  Add antenna tuner between the radio and antenna?   Add balun?  9:1?  49:1? 4:1?   

Any thoughts?  Tks 73s

4

Equipment / Re: Any way to modify noisy power supply?

« on: July 17, 2025, 1310 UTC »

The fan in the new switching psu seems to come on all the time even when the radio is off.   But when the radio is on, the fan gets louder and faster.
It seems to had been set to come on at certain temperature within the psu using some electronic programming chip in the factory?     But the output voltage seems to be solid.  The radios seem happy and on all day with no concern over the running out batteries like before when using the 8x AA battery pack.  When the input voltage from the psu drops to 12V or less, the radio gets noisy. At below 11V DC, the radio doesn't function properly.  It needs good solid 13V+ for working properly.  The new switching psu has no problem for providing the set voltage to any radios.

I am not going to open the psu and change anything because it would invalidate the warranty.

5

Equipment / Re: Any way to modify noisy power supply?

« on: July 12, 2025, 0809 UTC »

The new switching power supply is actually very noisy with the constant fan going in the psu.  And the digital meter reading on the front of the psu for current reading is not working.   Not ideal.

6

Equipment / Re: Any way to modify noisy power supply?

« on: July 10, 2025, 1148 UTC »

Making up 12V battery pack with 8x AA batteries were absolutely no use at all.  It powered on the radio OK.  But the radio draws about 500 - 600mW on standby.  The 8x AA battery power pack lasted about 1 hour, and then the radio died off.  I measured the voltage from the power pack, and it was 10V.  12V to 10V in one hour, and the radio needs new 8x AA batteries.   So, it would be ok for emergency use or for repairing 12V radios or devices for powering on for 30 min. to 1 hour, but no use for daily use of powering the radio.

I went to Amazon, and bought a new switching PSU 13.8V rated at Max 30A.  It does the job.  The PSU seems solid, accurate and quiet enough running the radio.  Hope it will last for years with no problems.  It would be handy later, when / if I decided to go for transmitting with HF / VHF transceivers too.

7

Equipment / Re: Any way to modify noisy power supply?

« on: July 03, 2025, 2124 UTC »

I once had an old linear power supply (made by quite famous company - but now cannot recall the brand). The power supply was 20A rated one 13.8V for full 100W Txing on amateur radios.  The psu was powering on an old ICOM IC-751 transceiver for just SWLing.

One day, the psu went bang with smoke and flames.  I quickly switched it off before it caught fire.  Luckily the IC751 was not damaged in any way, but the psu was totally damaged beyond repair.  I got it few days before the incident from eBay business dealer mostly selling used radio gear, and was able to return it for full refund.

After that, I am apprehensive about any linear power supplies, and even switching psu, they can blow any time  causing possible damage to the radios and even more.
Maybe it happened due to the age of the power supply, but then I just have this idea that it can happen to any power supplies.  I try to avoid using power supplies whenever possible.  They are also noisy due to the fans (if have them), and definitely noisier on the radios than battery powered radios.

But maybe it was just one off experience I had, and maybe they are safe to use I don't know. 

8

Equipment / Re: Any way to modify noisy power supply?

« on: July 03, 2025, 1104 UTC »

Thanks for your info and advice.  Yes, that looks a great filter for the psu noise problems.  But the price seems rather high for a filter.
If it were cheaper, it would be a very attractive device to add into the link.

But maybe I must try to implement battery pack for 12VDC made up of multiple AA batteries. 8x AA batteries are needed for 12VDC. Or buy a high quality psu?  WIll think for the options. 

9

Equipment / Any way to modify noisy power supply?

« on: July 02, 2025, 1752 UTC »

I have this Lab power supply made in China.  It has digital read out for voltage and also currents, and is fully adjustable continuosly via the dial from 0 - 30V, and it is rated 10A max.

It is great to power up project stuff, but when it is connected to SW radio, the radio gets noisy due to the power supply generated noise.  Is there any way to modify or implement something on the psu, and make it usable working with Shortwave radios?

10

Shortwave Broadcast / Re: 3310 kHz Radio Mojos Chaski from Bolivia

« on: June 26, 2025, 0955 UTC »

RX on this morning from scheduled recording via SDRuno software and RSPdx-R2 rig.
Rx ant is MLA30+ active loop.

https://www.youtube.com/watch?v=qi3AZpEpNUE

11

Shortwave Broadcast / 3310 kHz Radio Mojos Chaski from Bolivia

« on: June 25, 2025, 1642 UTC »

https://www.youtube.com/watch?v=kyK9vjQlUOE

Rx location: Scotland
Rx date: 25 June 2025
Rx time: from 0058 utc

Rx rig: SDRPlay RSPdx-R2
Rx ant: MLA30+ Active Loop

Not the best signal from the station copied herel, but quite audible.  Was able to hear the station every night recently.  With 5025 kHz Radio Rebelde Cuba, Bolivia is the most audible signal on the tropical band these days in my location of RXing which is Scotland.

12

Equipment / Re: Range of tolerated Output voltage from Active Antennas to Receiver

« on: June 23, 2025, 1310 UTC »

Not sure where the amp is made from, no names and no writings on the box.  But yes, it could be the antenna itself.  I am going to try with different length of the elements to see if it would make any changes in performance and also the DC leak into the radio antenna.

Some Chinese products seems quite good in quality and performance, but some are poor quality I agree.

13

Equipment / Re: Ideal thickness of wire for longwire antenna

« on: June 22, 2025, 1053 UTC »

Thank you for your points.  All noted.    Yes, you are correct in that I am only receiving, not transmitting.  I used to transmit on HF and 2M FM before, but transmitting can take too much time and effort and complexity, hence recently I am just RXing only on HF and MW and LW too.   Rx itself can be challenging and interesting in the complexities and things to try out and improve, and achieve, and it calls for a lot of time, energy and effort for now.  Maybe sometime in the future I might go back to transmitting on the HAM bands again, I don't know.  If I could have more time and finance to be able to afford all the right new and old gears for it, I might return QRV.

And I do agree with your point - 26 WAG wire would never be able to cope with transmitting RF unless extreme QRP.   For my 26WAG thin wire added to the existing LW (which was terminated at the window frame, and the new 26wag wire connected to it), it starts from my window upstairs radio room, and runs down to the garden shed, hence I can see it hanging in the space even if it is hardly visible usually, if I look at it with intense focus, I can see it.  The other day, the wire got loose for some reason, and was hanging very low nearly touching the ground.  I had to pull it from inside of the window and tighten into a plastic wire core securing to the old window frame, and now it is tightened and back up to the height.

For RXing, it seems doing well on 49m - 22m band, but for 60m band, my old MLA30+ does better for copying the Bolivia and Myanmar radio.  On these signals, it needs some amplification for RXing it seems.

Good DX and best 73s

14

Equipment / Re: Ideal thickness of wire for longwire antenna

« on: June 21, 2025, 1130 UTC »

Wire antennas with 91 balun seems to be doing great DXing job.  I am hearing Myanmar and South America, Cuba and many LPAM stations.  They are not great strong signals due to subdued HF condition during this summer sun lights, and intensified solar activities.  But at least they are audible via the wire antenna and radios.
I have added 20m long thin wire in 26 wag, and it seems to be definitely making positive difference in the reception.  I may add another 20m length soon.

15

Equipment / Re: Range of tolerated Output voltage from Active Antennas to Receiver

« on: June 21, 2025, 0943 UTC »

Sure.  Thanks for your great reply.  It has given me some understanding on what is happening with the Active Antenna and also radio antenna input.
I was using the old radios Kenwood R-5000 and R-1000.  They were not too happy being connected to the active antenna pumping out 3V DC.
The reception didn't sound right at all.  But they don't seem to have been damaged in anyway, as they went back to their usual good performance in reception when paired with the longwire and 91 balun.

Yes, I do need to investigate the active antenna further.