Allison KB1GMX has helped me out of numerous battles with recalcitrant amplifiers. She provided an interesting contribution on the r2pro mailing list thread that I referenced yesterday: <\/b><\/i><\/div>\n
<\/b> Interesting thread…<\/b>
<\/b> <\/p>\n I see Rick as <\/b>having provided the basis and tools and it up to the collective ‘US” to use them to <\/b><\/div>\n create that next generation radio. All you have to do is decide the performance and <\/b><\/div>\n then go about looking at the means to do so. All the blocks are there.<\/b><\/div>\n <\/b>
<\/div>\n Dynamic range, how much is enough? When I’m portable or mobile raw sensitivity is <\/b><\/div>\n more useful as the antenna is usually a compromise. Overload is easy to handle with<\/b><\/div>\n switchable attenuator. The exception to this was a radio designed for contesting in a <\/b><\/div>\n hostile <\/b>environment (a KW user 800ft away) if you burn power you get overload <\/b><\/span><\/div>\n performance. Its not a battery friendly radio (RX power is over 1A for headphone output).<\/b><\/span><\/div>\n Look at what you need and not what you want.<\/b><\/span><\/div>\n <\/b>
<\/span><\/div>\n TX power is just adding stages. I’ve worked MOSFETs, LDMOS, GaN FETS and there <\/b><\/span><\/div>\n are some pretty cool devices out there and some not designated for RF are cheap.<\/b><\/span><\/div>\n If all else fails the IRF510 gets both raves and derision. At 12V its a tepid device<\/b><\/span><\/div>\n but at over 20V and at 24V it starts to wake up and really perform. I’ve run The WA2EBY<\/b><\/span><\/div>\n design for a few years at 45W level using two of those push pull at 28V and its clean and <\/b><\/span><\/div>\n solid and the original pair are now over 6 years old! <\/b><\/span>I also run 8 of them (4x4push pull) <\/b><\/span><\/div>\n at 32V at 6M for a cool 210W with good IMD. <\/b><\/span>I’d add all the good (high gain, low IMD) <\/b><\/span><\/div>\n power fets perform better at 28 or 50V. For those into CW consider class E as I’ve <\/b><\/span><\/div>\n worked with this and using GaN fets have generated 15W with 82% efficiency at <\/b><\/span><\/div>\n 13.56mhz (includes driver and osc) and using the lowly IRF510 at 12V a full 10W <\/b><\/span><\/div>\n with 85% efficiency. Class E can be amplitude modulated.<\/b><\/span><\/div>\n <\/b>
<\/span><\/div>\n As to the thermionic FETs, a 6AU6 crystal osc driving a 5763 for 10W gets a lot of raves<\/b><\/span><\/div>\n on 40M from a buddy that runs CW. The same deal plate modulated can sound good <\/b><\/span><\/div>\n at 5-6W AM on 75M. For those that want more a 6C4, 6aq5, 6146 will get you over <\/b><\/span><\/div>\n 50W on CW and 25W AM. Change the bias a little and inject IQ SSB into the driver grid<\/b><\/span><\/div>\n and be running 50-80W PEP. A 12BY7 or 6CL6 driving a pair of 6146 will get you into <\/b><\/span><\/div>\n the 180-200W DC input range for about 100W. Remember the hybrid radios solid state <\/b><\/span><\/div>\n low <\/b><\/span>level and rugged tubes for the heavy lifting. The Pi network (or Pi-L) will load anything <\/b><\/span><\/div>\n from <\/b><\/span>about 28 to 100ohms more if you use enough taps and variable caps. That and DC-DC<\/b><\/span><\/div>\n converter for the HV are not terrible at 80% or better (even the 1960s transistor designs <\/b><\/span><\/div>\n were better than 75%).<\/b><\/span><\/div>\n <\/b>
<\/span><\/div>\n In the end it all starts with the receiver. For that you can always start with a 1T4 RF and <\/b><\/span><\/div>\n a 1R4 converter and a 1T4 as regen driving a 3V4 audio. Power it with 45V (five 9V battery)<\/b><\/span><\/div>\n and a C cell and go portable. It should run for a very long while. Hollow fets run well at low <\/b><\/span><\/div>\n drain currents. \ud83d\ude42<\/b><\/span><\/div>\n <\/b>
<\/span><\/div>\n Allison<\/b><\/span><\/div>\n
<\/b><\/span><\/i><\/u><\/sub><\/sup><\/strike><\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"Allison KB1GMX has helped me out of numerous battles with recalcitrant amplifiers. She provided an interesting contribution on the r2pro mailing list thread that I referenced yesterday: Interesting thread… I see Rick as having provided the basis and tools and it up to the collective ‘US” to use them to create that next generation radio. … Continue reading “Design Wisdom from Allison, KB1GMX”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[84,126,101],"tags":[],"class_list":["post-2647","post","type-post","status-publish","format-standard","hentry","category-amplifier-theory","category-campbell-rick","category-tubes"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2647","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=2647"}],"version-history":[{"count":0,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2647\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=2647"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=2647"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=2647"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}