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LDG RU-1-1 1:1 Unun problem

[email protected]
 

The winter before this one when I got my HF rig set up, I noticed I got all kinds of interference when my furnace kicked in. Someone suggested this RU-1-1 unit might help. I didn't really notice any difference with or without it, so it's been sitting in a closet ever since.

I was moving some stuff around yesterday and decided to hook it up just because why not.

On 40 and 20 meters I'm not sure how much difference there really was but I didn't notice any drop in performance. On 10 meters though as soon as I try to key up my IC7300 the SWR is through the roof. Is this model not usable on 10m??
 

The 1:1 unun really won't help with external interference.? What it can do, is reduce RF coming back into your radio, and possibly help reduce interference in the shack.? One good use would be radio=>1:1 unun=>coax (for counterpoise)=>49:1 Unun=>EFHW.

What you need to reduce the interference from your furnace is Mix 31 ferrites on the power wires to your furnace, and/or blower fan.
According to the specs online, the 1:1 is rated for 200w 1.8-30mhz.? It should?not affect SWR being in or out of the circuit (much, if any), but additional coax can always change the reading.

Hope that helps.
Paul - Ka5pmv

On Mon, Apr 3, 2023 at 3:02?AM <gregp74@...> wrote:
The winter before this one when I got my HF rig set up, I noticed I got all kinds of interference when my furnace kicked in. Someone suggested this RU-1-1 unit might help. I didn't really notice any difference with or without it, so it's been sitting in a closet ever since.

I was moving some stuff around yesterday and decided to hook it up just because why not.

On 40 and 20 meters I'm not sure how much difference there really was but I didn't notice any drop in performance. On 10 meters though as soon as I try to key up my IC7300 the SWR is through the roof. Is this model not usable on 10m??

 

I just bought one of these last week. Should have believed OP.? This Ldg 1:1 unun makes 10 and 12 m band swr so high the ic-7300 cannot tune it out. 15m is also worse than without it but at least tuneable. Perfectly fine in other bands.
 

I have the same choke brand new in box sitting unused because it creates an SWR problem from 20m and up. I checked it with a nanoVNA and dummy load, and what should be an invisible-to-RF-output component is showing significant SWR from 14mhz to 30mhz. A different manufacturer’s choke that I bought to replace it has a flat SWR response across the HF spectrum.?
 

Maybe the wrong ferrite material type in the core was used in a manufacturing run? Has anyone approached LDG about this?


On Thu, Nov 7, 2024 at 6:31, Glenn Butzlaff
<gbutzlaff@...> wrote:
I have the same choke brand new in box sitting unused because it creates an SWR problem from 20m and up. I checked it with a nanoVNA and dummy load, and what should be an invisible-to-RF-output component is showing significant SWR from 14mhz to 30mhz. A different manufacturer’s choke that I bought to replace it has a flat SWR response across the HF spectrum.?
 

At 06:31 AM 11/7/2024 -0800, you wrote:
I have the same choke brand new in box sitting unused because it creates an SWR problem from 20m and up. I checked it with a nanoVNA and dummy load, and what should be an invisible-to-RF-output component is showing significant SWR from 14mhz to 30mhz. A different manufacturer s choke that I bought to replace it has a flat SWR response across the HF spectrum.
I had the same problem.

I re-wound mine the way I think it should have been, and now it's flat
into a 50 ohm load all the may up to two meters.

KB7ADL
 

/g/ldgelectronics/topic/99390381#msg1395?

here is a movie I did on the subject?
https://www.youtube.com/watch?v=QZq2M5Hsj2U
 

This inspired me to test my LDG unun. I always just "assumed" the 1:1 was transparent to the bands it was rated for. LDG says it is good for 1.8 to 30 Mhz. I know that when I tried using it on 6m it rendered my otherwise resonant antenna unusable.
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Here is my NanoVNA going to a short piece of coax and then into a 50 ohm resistor.
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Here is the same 50 ohm resistor with the unun at the end of the coax. Above 11.4Mhz it's 1.5 SWR
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Here is what the windings inside look like. I count 12 windings
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Vince, how did you change the windings, could you post a picture? Is it just half one way, then cross over and then out the other side, how many windings did you do?
Something like this?
?
 

I rewound mine today, it was a bit difficult to get good/tight windings with the existing wire being kinked already and it is not perfect, but it did improve the SWR a little. I would not say it is great still, but it is improved.
You could probably get much better results using fresh magnet wire, or 2 conductor wire that keeps the spacing more consistent, or better yet some RG316 coax.
?
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