Filter modulator card - version 1a modifications

[g8gtz]

The team has been looking at ways to improve spectral purity and has come up with a couple of simple modifications to the current design.

The PCBs sold before February 28th (ie all of the current boards) are known as Version 1 boards and are OK to use on-air as any spurious emissions are about 50 dB below the main transmission, and the modulation "shoulders" will generally be in-band. However, there are a few modifications that can be done to improve their output and reduce the level of the "shoulders" at SR1000 and above. The modifications also equalise the levels between low SRs (RB-TV) and higher SRs (1000 and above).

Details of the board revisions and modifications to bring the board to "Version 1A" standard along are available on the wiki https://wiki.batc.tv/Filter_Modulator_build

[M0SKM]

Have any spectrum images been published on the forum or wiki?

I've not found any and would like to compare my Portsdown with standard specifications.

Perhaps spectrum analyser results produced during team tests could be posted on the wiki.

Great project thanks and I'm sure it's on a list of to do's.

Steve

[G8GKQ]

Hi Steve

Yes, we have some spectrum plots, but realised (too late) that our "before" and "after" plots were taken with different frequency scales. We are meeting up this Friday to resolve the issue and hope to get them published at the weekend.

Dave, G8GKQ