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6m Larcan Conversion

Here's how John K4DLX modded the input and output connectors.

73, Bill NZ5N
 

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At DC or 60hz it will be fine. At 50 MHz that is another story. The contact rating is not the issue. The lead length of the wire is.




Agreed.There are ways to change that relay by cutting the wires off that go to the common ports and soldering jumpers across a pair of contact levers so that the normal operation of DPDT is retained but the contact arrangement is different and the lead length is very short compared to what it was before being modified. Looking for a link to a picture of it as I write this. One such mod is in an older issue of the ARRL handbook and is shown on a homebrew 2m amp.

at 50 mhz any strange multiple of wavelengths will be avoided with such a short connection. If we were any higher I'd be worried. besides you could just use a bit of coax as suggested here. I think he will be fine.
 
Lead length per-say is not the issue but rather the Stray capacitance and inductance they offer. I had a switch box that was unusable on 6m until I removed the leads and used small coax cable instead.
I also saw an amp where hand Capacitance was enough to detune it. Things start to get fussy on 6m.
 
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I was thinking about using a fixed external ALC voltage independent from any rectified RF based source but may opt for the same type attenuator Michael is using from Florida RF Labs. Those are great little devices.
 
while your idea is much more efficient and high tech i find mine fool proof and alot simpler for me personally, another member also mentioned that some radio (such as the ft 847 which i have) has an internal power adjustment that can cap you output, which is also a viable option.
 
Most any radio can be rolled back to 5 or 10 watts out. My FT-857 will go to 5 watts but when set at that level still has a power spike upon keying up that far exceeds that. With an external ALC voltage it does not and that is why I was thinking about that method. I would have it such that the ALC voltage was applied the instant the amp was powered up. I just don't like running the rig at full output for only 10 or so watts of drive. It's not 100% foolproof but what in life ever is. ;)
 
Here are a few pictures of how I am doing my output. Instead of bothering with a connector, I am just attaching a piece of LMR400 Flex directly to the amplifier, then going into the LPF and Dow Key. Saves a connector on the amp and one on the jumper that is going to be there anyway. I am going to add a clamp on the bottom to hold the LMR 400 more safely.
 

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Here are a few pictures of how I am doing my output. Instead of bothering with a connector, I am just attaching a piece of LMR400 Flex directly to the amplifier, then going into the LPF and Dow Key. Saves a connector on the amp and one on the jumper that is going to be there anyway. I am going to add a clamp on the bottom to hold the LMR 400 more safely.


Those look like the relays I am going to use except mine do not have the auxcilliary contacts on the side. mine are Dow Key with type N connectors.What are you guys going to use as a LPF? I haven't given that aspect much thought. Been too busy trying to get the entire HF/6m/2m antennas and grounding etc. done. Lots of work here doing a complete and total tower/antenna rebuild from the ground up. Literally.

Just added a pair of 13B2's to my antenna arsenal BTW. They should be here tomorrow.
 
while your idea is much more efficient and high tech i find mine fool proof and alot simpler for me personally, another member also mentioned that some radio (such as the ft 847 which i have) has an internal power adjustment that can cap you output, which is also a viable option.
I mentioned the internal power adjustment in the FT-847 but was later informed that this does not stop the spike, the only way to get rid of the spike is to perform this mod:
ALC_FT847_cz_cast.2

I have not yet tried it but it seems fairly easy.

73, Bill NZ5N
 

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