Nice try 👍🏻. As someone who has used this receiver for a long time, I can confirm that it makes a very decent desktop receiver when coupled with an external antenna. Not worse than radios five times more expensive. The issue is that it has an HF preamp built-in already (J8 transistor), not just missing hardware band filters, so anything like a long-wire antenna or (especially!) an active/MLA-30x antenna will simply overload it. It was designed to receive as much as possible on its own whip antenna, and that's it. To avoid heavy modifications, I simply connected an external passive loop antenna through an HF transformer (1:2±9 -> this can be identified only through testing, depending on coax cable length, antenna specs, etc.). BOTH antenna IN and GROUNDING (-) have to be used to connect the first coil of the HF transformer through the cable. The first coil has to be fully decoupled from the second coil. More thorough modifications could include removing the preamp and connecting an active antenna directly.
@RJDA.Dakota Жыл бұрын
One SW radio I had did use a very unique antenna situation: A Realistic Astronaut 4: it had a whip antenna which would work on both the shortwave bands and the medium wave loops antenna which the manufacturer said in the manual that it would work up to 10 MHz. Many manufacturers had similar designs for their products. I thought that was unique for the time.
@F4LDT-Alain11 ай бұрын
Very interesting and instructive video, thanks. May I ask what kind of "real antenna" you were using at your window? I presume not an MLA30.
@sfred
11 ай бұрын
A reel antenna, like the Sangean ANT-60.
@F4LDT-Alain
11 ай бұрын
@@sfred Oh 😁 "reel" not "real", I misunderstood (not native English speaker here). Thanks for the information.
@robmccarthy1018 Жыл бұрын
Good vid sfred. It seems that most modern SW portables suffer from AM or FM overload from strong local stations.. I guess they don't have proper front end filters etc I enjoy your videos and you may be able to help me.. I notice you're using an MLA30+ loop. I've never seen one in real life. The output appears to come from the amp box via coax to receiver. I notice (as do many folks) you connect the loop to the whip antenna. How do you get on with this as there's not a balanced input to the receiver? Or is there an unbalanced wire o/p from the box? Appreciate your wisdom as i'm thinking of getting an MLA30+ online. Cheers Rob
@sfred
Жыл бұрын
The small DSP radios seem to be the worst for this, but I also see it in my analogue portables too. For most people it's never going to be an issue, but for people in line-of-sight of major FM transmitters it's just one of the things we have to deal with. For my radios with an antenna jack I use an adaptor from the coax to a 1/8" mono plug. On those, the shield is tied to the sleeve of the 1/8" plug. Of the radios without an antenna input, I've been using an adaptor that goes from a 1/8" jack to the antenna clip. Those things just connect to the tip of the plug to the clip and leave the sleeve floating. I'm not actually sure how the coax behaves when you do that, but it might explain some of the FM overload problem. That might be something to investigate in a future video.
@robmccarthy1018
Жыл бұрын
@@sfred Thanks for your thoughts. Is the ext ant. socket on my D808 actually coaxial? The antenna lead that came with it just ia a single wire with a mono plug on it. My good old cleaned up and realigned 1970s Realistic DX-160 works great on a long wire (mine is 50 feet up into a tree) Even tho' it's image rejection on the higher end isn't too good (single conversion) it's fully tuned (3 gang caps) JFET RF AMP with separate JFET mixer and JFET local oscillator doesn't suffer from overload. This good old all analog receiver is just as sensitive as my Tecsun S2000 and a bit less noisy. The bandspread is great and it has adjustable AGC, Noise, Noise limiter antenna trim and BFO with proper product detector. Sigh. If only it had the freq read out and stability of the modern stuff. I had an R1000 in the 80s and loved it 🥰
@sfred
Жыл бұрын
@@robmccarthy1018 I've no idea how the D808 is set up. Without a schematic or opening in up I'm not sure how you'd tell. The DX-160 sounds great!
Пікірлер: 9
Nice try 👍🏻. As someone who has used this receiver for a long time, I can confirm that it makes a very decent desktop receiver when coupled with an external antenna. Not worse than radios five times more expensive. The issue is that it has an HF preamp built-in already (J8 transistor), not just missing hardware band filters, so anything like a long-wire antenna or (especially!) an active/MLA-30x antenna will simply overload it. It was designed to receive as much as possible on its own whip antenna, and that's it. To avoid heavy modifications, I simply connected an external passive loop antenna through an HF transformer (1:2±9 -> this can be identified only through testing, depending on coax cable length, antenna specs, etc.). BOTH antenna IN and GROUNDING (-) have to be used to connect the first coil of the HF transformer through the cable. The first coil has to be fully decoupled from the second coil. More thorough modifications could include removing the preamp and connecting an active antenna directly.
One SW radio I had did use a very unique antenna situation: A Realistic Astronaut 4: it had a whip antenna which would work on both the shortwave bands and the medium wave loops antenna which the manufacturer said in the manual that it would work up to 10 MHz. Many manufacturers had similar designs for their products. I thought that was unique for the time.
Very interesting and instructive video, thanks. May I ask what kind of "real antenna" you were using at your window? I presume not an MLA30.
@sfred
11 ай бұрын
A reel antenna, like the Sangean ANT-60.
@F4LDT-Alain
11 ай бұрын
@@sfred Oh 😁 "reel" not "real", I misunderstood (not native English speaker here). Thanks for the information.
Good vid sfred. It seems that most modern SW portables suffer from AM or FM overload from strong local stations.. I guess they don't have proper front end filters etc I enjoy your videos and you may be able to help me.. I notice you're using an MLA30+ loop. I've never seen one in real life. The output appears to come from the amp box via coax to receiver. I notice (as do many folks) you connect the loop to the whip antenna. How do you get on with this as there's not a balanced input to the receiver? Or is there an unbalanced wire o/p from the box? Appreciate your wisdom as i'm thinking of getting an MLA30+ online. Cheers Rob
@sfred
Жыл бұрын
The small DSP radios seem to be the worst for this, but I also see it in my analogue portables too. For most people it's never going to be an issue, but for people in line-of-sight of major FM transmitters it's just one of the things we have to deal with. For my radios with an antenna jack I use an adaptor from the coax to a 1/8" mono plug. On those, the shield is tied to the sleeve of the 1/8" plug. Of the radios without an antenna input, I've been using an adaptor that goes from a 1/8" jack to the antenna clip. Those things just connect to the tip of the plug to the clip and leave the sleeve floating. I'm not actually sure how the coax behaves when you do that, but it might explain some of the FM overload problem. That might be something to investigate in a future video.
@robmccarthy1018
Жыл бұрын
@@sfred Thanks for your thoughts. Is the ext ant. socket on my D808 actually coaxial? The antenna lead that came with it just ia a single wire with a mono plug on it. My good old cleaned up and realigned 1970s Realistic DX-160 works great on a long wire (mine is 50 feet up into a tree) Even tho' it's image rejection on the higher end isn't too good (single conversion) it's fully tuned (3 gang caps) JFET RF AMP with separate JFET mixer and JFET local oscillator doesn't suffer from overload. This good old all analog receiver is just as sensitive as my Tecsun S2000 and a bit less noisy. The bandspread is great and it has adjustable AGC, Noise, Noise limiter antenna trim and BFO with proper product detector. Sigh. If only it had the freq read out and stability of the modern stuff. I had an R1000 in the 80s and loved it 🥰
@sfred
Жыл бұрын
@@robmccarthy1018 I've no idea how the D808 is set up. Without a schematic or opening in up I'm not sure how you'd tell. The DX-160 sounds great!