In reply to 2W0NNN:
If, however, you want effectively a lot more dBs for the price of a key
Just how many more?
Well we can do some very crude power spectral density (PSD) maths. This is the “back of a fag packet” version not the proper PSD. It’s 30 years since I last had to work one out and I’m a bit rusty at the hard sums involved.
But an informative value of the benefit of CW can be had doing the following for an 817. Output = 5W, CW TX b/w = 100Hz, SSB TX b/w = 2700Hz
CW: 5W/100Hz = 0.05 W/Hz
SSB: 5W/2700Hz = 0.00189 W/Hz
So CW has approx 27 times higher PSD. This assumes the power is spread linearly across the TX b/w and it certainly isn’t for voice. But I did say it’s the informative not accurate version.
Or in simple terms to sound as “loud” as a 5W CW signal you need to have about 135W of SSB. We’ll round things about and say 5W CW approx. 100W SSB.
There’s no doubt that 20W for SSB makes noticeable difference over 5W even though it’s only 1S point. The real problem of low power SSB is that it’s hard to protect your frequecny from an alligator who’s all mouth and no ears and splats all over you. This is mitgated if you’re lucky enough to get a well equipped chaser who will come on your freq. and drive the encroaching stations back.
A speech processor is a noticeably missing from the 817 and having an outboard one makes a big difference as it ups the PSD. I’d add one of those before I’d add an amp. Not very heavy and doesn’t need a big extra battery.
For the higher bands, more antenna gain is reasonably easy to get. A vertical Moxon for 15/12/10m is not a massive antenna and gives good improvement. It weighs less than an amp and improves RX as well as TX.
If you have an 817 the improvements in order in my view would be
- learn enough (*) Morse to have SOTA QSOs
- make a better antenna
- add an outboard speech processor.
- make an amp
- sell the 817 buy an 857 and new batteries
For those who aren’t aware, the MX-P817 is a 50W addon HF amp which interfaces to the 817 and uses the automatic bandswitch data to follow the 817. It’s got filters unlike that RM CB trash and uses a nice Motorola FET. You can get them for between £135-£170 depending where you look.
In the meantime Gerald, how did your 1st CW lesson go last night?
Andy
MM0FMF
- My CW skills are sufficient to get a callsign and report and the GA ANDY at about 18-20wpm. If someone wants to send me plain text then we need to drop to about 10wpm or slower. You don’t need to be character perfect for extended receiving at 30wpm for SOTA.