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Re: [TowerTalk] Soldering Coax Connectors

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Soldering Coax Connectors
From: Martin Sole <hs0zed@gmail.com>
Date: Fri, 6 Sep 2019 12:10:02 +0700
List-post: <mailto:towertalk@contesting.com>
I've been soldering coax connectors for years, mostly N type and BNC clamp type. I've probably done several thousands of both as well as PL259 and SMA, SMB types. The iron is absolutely key in all of this and a simple watts rating is no way to assess the iron. Tip temperature and thermal mass are I believe far more important. You want the right amount of heat applied in such a way that it raises the temperature of the parts very quickly to that required. As you leave the tip of the iron on the work for longer the heat spreads out melting things as it go's.

Today I use a JBC soldering station but I think the brand is not so important, there are a few that can do the job. Tips used range from a tiny fine point that can reach into the weep hole of an N type to a chisel head that allows almost plumbing sized connections. Tips can be changed on the fly with the extractor plate and time to reheat is about 5 seconds. Time to temperature from standby is almost instantaneous.

I pre-tin the centre conductor and then cut down to size. The right technique allows just the right amount of tinning such that the centre conductor will still enter the pin. Heat is applied close to the weep hole, not on it and then solder is fed in at the weep hole. Capillary action draws the solder into the pin and together with the pre-tinned centre conductor requires literally a second or two of heat application. Tip temperature never drops below the preset temperature, usually around 300-320 degrees C for these jobs.

Over-sizing the pin with excess solder is a common problem usually due to insufficient immediate heat and excess solder. I'm sure its not a "recommended" technique but I don't think for most uses dressing the pin with a fine file to remove any excess is a big problem but with practice and the right tools it soon becomes a non-issue.

Martin, HS0ZED



On 06/09/2019 10:56, Gedas wrote:
I use crimp and traditional clamp type of connectors. I have a question on the proper way or technique that should be used to solder the center pin of N, BNC, and SMA style connectors onto the coax center conductor w/o making a mess.

I do not have any issues with connectors like PL-259's or pure crimp type connectors but I still struggle to solder just the center conductor of the coax to the center pin w/o making a small mess on the outside of the center pin and w/o melting the dielectric. I use a 25W Weller for the center pin and have tried various tips. I also have tried different solder sizes down to those ideal for SMD work.

How do folks get solder to flow just into the weep hole ? Do you use a tiny pointed tip iron and put that tip into the weep hole and hold it there until the center pin gets hot enough to melt solder? If so do you then keep the iron in the weep hole and dab solder at the tip/pin interface and hope it gets drawn in? Or, do folks use a larger sized iron tip underneath the center pin to heat it up enough so that solder when pushed into the weep hole will melt and cause a good connection?

What about pre tinning the center conductor?

Either way, regardless how careful I am, more times then not I seem to get residual solder all over the outside of the center pin and need to carefully scrap it off with an X-acto blade after things cool off.

And then of course there is the problem with holding the larger iron tip under the center pin too long and start melting the dielectric because the center conductor has been over heated.

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 9/5/2019 11:07 PM, Bert wrote:
I always solder the pin, regardless!

Bert VE3NR


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