Wondering how to increase the voltage on the final of the BITX40, I decided to try an up converter, started to search on Ebay and found some very cheap units that seem far to small to do the job (3-5-30V-to-4-0-30V-DC-DC-Booster which are only 50mmx40mm), but are so cheap that I had nothing to loose, I chose a slightly more expensive site in UK so that I did not have to wait for delivery from China, you can see the unit on the link below,
http://www.ebay.co.uk/itm/New-3-5-30V-to-4-0-30V-DC-DC-Booster-Converter-Step-Up-Voltage-Regulator-LM2587/272041590361?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D40762%26meid%3D18dbdcfbce2c4a8c95e9904a1da366c2%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D122175575738
Have now installed it and after adjusting the output voltage to 24v and still using the original 100ma bias was surprised to now see that the output is 20watts
Have checked the output voltage under load ( Loud Hello) and found that the regulation is excellent went down to 23,5V
Certainly worth a go for ?3 /$4 and free postage
73
John mi0dfg