June and the Joy of the Junk Box

I'm having a break from my WSPR project while I wait for more parts to arrive. But I couldn't go cold turkey so I rummaged through the junk box and one of the many boards I pulled out is shown below. And it got me thinking. What could I use this for? What parts could I re-use? Is it really worth keeping?

The board has some nice helical coils used for filtering so it was probably the UHF variety of Motorola Syntrx radio. These helical coils are presumably high Q and perhaps could be re-used. I measured the dimensions and if the free end was unwound and used as a could they would appear to around 130nH. Some quick number crunching suggests that might be useful for front end filtering at 6m and 2m.

I pulled one out, unwrapped half an turn from the floating end and inserted the resulting coil into my inductance measuring fixture. The measured inductance turned out to be 141nH with a Q of 160. Popped that all into some filter software which showed that at 2m a 3 pole filter would have a loss of about 1.2dB. That's about 0.4dB worse than a 2 pole filter but perhaps the slightly higher attenuation of pagers would be worth the extra loss and complexity.

2m Filter, 2 poles (dashed) versus 3 poles (solid)

The issues at 2m are the inductance makes for very small values of capacitance. Not insurmountable though. Having removed all the helical coils from the board the space available does have me intrigued to give it a go.

Then why I was playing with the Iowa Hills software I noticed a red message: "First Tank Z is Large". I re-ran the design in Elsie and then realised that in practice the message meant the coils were too large.Then I discovered the series option in Iowa Hills. This is not something I had ever seen before in Elsie or AADE. It gave me a design, after tweaking, like the following (shown in comparison to the previous 3 pole topology):

I worked out how I could manually tweak the capacitor values to what I wanted and found that as long as the parts were close to design I wouldn't need trimmers. Since I've never built a filter like this I decided to see how well it worked in practice. Over the next week or so I will build this and report back on the results.

I have a project in mind for the filter and board. Anyone else have thoughts on what it could be used for?

Regards
Richard