Reducing Noise on Alinco DX-r8t/E & Wellbrook ALA1530 Antenna

Status
Not open for further replies.

KC1CJN

Member
Premium Subscriber
Joined
Jul 8, 2014
Messages
16
I have set up my ALinco DX-r8t/E SWL receiver in my 3rd floor office, connected to a Wellbrook ALA1530 active loop natenna, which sits on my window sill. I have no other options for an antenna, as I can run wire outside the building or outside my office.

I have a 3ft 12G solid copper wire from the ground terminal to a radiator pipe, and am beginning to put Mix31 ferrite beads on all of the electrical wires and PC cables in my office.

While AM comes in clear, HF (20m, 17m) is very noisy, and I can barely make out any voice. Even WWV 10.0 MHz is very noisy at 4am, when I can get a loud and clear signal from my mobile.

The window faces another 4 story building and I only get a gap of sky, so signal is probably poor.

Are there any other options I might try to cut noise and boost signal (within the office walls)?
 

ridgescan

Member
Joined
Apr 1, 2008
Messages
4,778
Location
San Francisco, Ca.
Is that ground wire from that radiator going to the loop or the radio, and how are you feeding the loop-with 50-75ohm coax?
I would personally feed the loop with 75ohm triple shielded coax and not use that ground to the radiator. Also, if your window frame is metal, it likely has a ton of RFI riding on it and your loop may do better away from it. A little trial and error is in order in your very tough setting. Maybe running the loop further inside it will still catch signals as HF isn't quite so line-of-sight like VHF and above and that loop is quite "active". Try stuff.
 

k9rzz

Member
Joined
Dec 12, 2005
Messages
3,162
Location
Milwaukee, WI
What kind of noise? Buzz, hiss, roar, hash, digital? Always the best cure is to eliminate the source. If you're wedged in between two concrete and steel buildings and getting low signals, there isn't much you can do outside of getting out of that confine.
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
25,361
Location
Bowie, Md.
First off, that radiator pipe can't really be that good a ground - as it expands and contracts due to temperature change, it will cause some noise, assuming you have it connected with something along the lines of a hose clamp. In addition, being on the third floor, there's no way in hxxx you can guarantee that pipe is a proper ground - it probably winds its way throughout the building, and you can't guarantee the (electrical) quality of each joint in the entire system. Under some circumstances, it might even be acting as a antenna instead of a ground...Probably better without it, frankly.

Hopefully you are also looking at the power supply for the Alinco - make sure that's got some ferrite beads or is choked off.

I would move that antenna away from that window and choose another location that is not facing another building, if at all possible. I would wager that you're getting blasted by all the RF radiating from that opposing building, not just the RF from within your own office. Mike
 

SCPD

QRT
Joined
Feb 24, 2001
Messages
0
Location
Virginia
What kind of noise? Buzz, hiss, roar, hash, digital? Always the best cure is to eliminate the source. If you're wedged in between two concrete and steel buildings and getting low signals, there isn't much you can do outside of getting out of that confine.

Agreed.
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
25,361
Location
Bowie, Md.
Quite so, but he can't put anything outside (no real surprise there, unfortunately)

If it were me, I'd take that setup home and get an account with Global Tuners and/or one of the online SDRs....far less hassle than what the OP is going through now....Mike
 

KC1CJN

Member
Premium Subscriber
Joined
Jul 8, 2014
Messages
16
Mostly hiss.

Yeah, I'll try w/o the ground to pipe and move the loop away from the window frame.

And using 50ohm RG8X coax.
 

SCPD

QRT
Joined
Feb 24, 2001
Messages
0
Location
Virginia
Mostly hiss.

Without any audio or video samples there's no way to know what you're hearing.

Yeah, I'll try w/o the ground to pipe and move the loop away from the window frame.

I doubt this will make any difference. The loop is amplified and RFI will hit you from just about everywhere.

Since the "hiss" is strong enough to to affect your 20m listening then it's likely a source coming from your office. It could be TVs, lighting (touch lamps), wall warts, laptop chargers, etc. Anything that uses MAINS power is going to be suspect. Most office buildings have quality (commercial-grade) grounding and MAINS power isn't likely to be dirty; however, older buildings may be more at risk of bad wiring and/or bad power regulation.

If you're really serious about listening from that location then you should pick up shortwave portable and then you can use that to sniff around the office/floor and find out what the offending source is with its stock antenna.

From my experience, you'd be surprised how a single noise-generator can wreak havoc on your listening experience.
 

k9rzz

Member
Joined
Dec 12, 2005
Messages
3,162
Location
Milwaukee, WI
I think the real answer is to somehow suck some signal from outside your confines. Either get something up on the roof (probably impossible) or do it the sneaky way like clamp on to a fire escape, metal flashing, or down pipe of some sort on the outside of the building. Poke your head out the window if you can and see what's out there. Last resort would be to drop a wire down out the window and just reel it back in when your listening session is done. Even if it's 30 guage magnet wire, just as long as it's strong enough not to break. That sometimes works.
 

KC1CJN

Member
Premium Subscriber
Joined
Jul 8, 2014
Messages
16
Either get something up on the roof (probably impossible) or do it the sneaky way like clamp on to a fire escape, metal flashing, or down pipe of some sort on the outside of the building. Poke your head out the window if you can and see what's out there..

Hmmm... 3ft diameter steel furnace vent running from ground up to stack on roof just 10ft from my window. Can I swing a wire with magnet over to it and use as an antenna?

They have window cleaners on lift out twice yearly, or I'd shoot a stealth wire out over the next building's roof...

[EDIT} Ahh - I realized the magnet wouldn't be holding up the wire antenna, as the steel vent is supposed to be the antenna. I never thought about it, but I suspect RF doesn't pass through a magnet to well without deleterious effects, eh?
 
Last edited:

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
25,361
Location
Bowie, Md.
No, magnetism really won't affect RF, and in fact, in certain conditions - like in a so-called longwire balun, magnetic coupling is actually beneficial...

Any of those solutions are worth trying, though I suspect the RF field around the building will be so dense that a wire close to the building is still going to get swamped with noise.

If you are going to use a wire outdoors, I'd feed it through a 'longwire balun' then follow that with coax. There are many designs for 'magnetic longwire baluns' (more properly, 9:1 transformers) on the net, and they don't look to be too hard to build.

Mike
 

ratboy

Member
Premium Subscriber
Joined
Nov 3, 2004
Messages
970
Location
Toledo,Ohio
I work in a building full of PCs and 2 huge rooms full of racks of servers, and HF reception is pretty much a joke. Even low band VHF is pretty well trashed. I have found nothing to make it much better, except for one odd thing. I have bought a lot of old receivers on Ebay and I will take them to work for clean up, repairs, etc, and I found out when cleaning up my Kenwood R1000 that if I take the top of the case off, and touch pretty much anywhere along the signal input path, reception improves to the point that at least the radio can be listened to for check out purposes. This has worked for many reciever models. It's still trashed from all the hash, but you can hear something. If I don't do this, I literally cannot hear anything except a very few stations and some local broadcast band stuff. My first Icom R71A was so bad here, I thought it was defective, but home on the kitchen table, it was great. Obviously, don't try it with a tube set!
 

nanZor

Active Member
Joined
May 28, 2009
Messages
2,807
A few things come to mind ----

A "shielded loop" needs to be clear of surrounding metal objects and rotatable to put noise in the null. The rejection comes from directivity, and if the loop is close to other metallic objects, then it becomes unbalanced, and the directional null is lost.

While I know you can't put it outside, perhaps backing it away from the window and a bit inside away from the metallic frame (possibly covered but still there on the interior) may help.

What are you using to power it with? A clean dc supply, or perhaps a noisy switching supply?

Is the amp on the loop overloading the R8t? Have you tried different settings of the preamp / attenuator?

Also just forget trying to use the noise-blanker with the Alinco. Pretend that button isn't even there.

Is your IF shift centered, or just a *smidgen* off-center (depending on lsb/usb)? The R8T's if shift is very sensitive and doesn't need much rotation. While mine is packed away, I think there is also an option to swap the if-shift with something else, which could affect ssb if rotated too far. (I need to check the manual when I can)
 

nanZor

Active Member
Joined
May 28, 2009
Messages
2,807
I must be on an active antenna binge ... :)

You may also want to put a ferrite choke, like an MFJ-919 or similar inline with the loop. OR, if it doesn't cut off any dc supply sources, a galvanic breaker / isolator, like an AOR GT-1 or other airwound isolation choke ....
 

wb6uqa

Member
Joined
Aug 16, 2015
Messages
352
Location
Santa Monica, Ca.
noise

first if your furnace is gas you can cause a explosion. Never ground to a gas pipe. Use a quarter wave wire to your radio for each band, they can be bundled <ground>. Use your loop to locate the direction of your noise. unplug everything in your office and check for noise. good luck Call your power company.
 
Status
Not open for further replies.
Top