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Only ones I know of are the Hardrock-50, HFpacker and the WA2EBY. All but the last one are total kits and cost 300+ I just built up a WA2EBY amp and am pretty happy with it so far. I got the pcb's from Toroids Build notes I would suggest if you choose the WA2EBY option be sure to do a proper parts list as the on from the link in the build notes is a bit outdated. ? ? 73 ?? GL ?? David ??? N8DAH |
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John McFadden
Sorry for the newbie question, but the WA2EBY kit is for 1W drive, won't that splatter like crazy with 5-10W from a uBitx? Or how would an operator decrease the uBitx output power that low to let the amp work?? John On Jan 10, 2018 10:24 AM, "N8DAH" <Dherron@...> wrote:
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On Wed, Jan 10, 2018 at 9:39 AM, John McFadden <johnamcf@...> wrote:
A 7dB (5x) resistive pad on the amplifier input should reduce the input power sufficiently. Alternately, you could adjust the bias current on your uBitx so that it only puts out 1W. -Neil N0FN |
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Yep pretty much as Neil N0FN has said. ? On the schem R8,R9 and R10 are a pad for the input (remember to cut the trace at R9 if you install the pad). I am running the bitx40 with a 5w pad installed. I have set my bitx40 for 5W key down CW so max I get is 5W. I will be using this setup with my Ubitx as soon as I get it and have it running. I plan to set the out at 5W on that as well, it just works better for my setup. ? It may not be a fit for you but its a viable lower cost option, if memory serves total cost was around 100$ after parts and shipping. I have had a Hardrock-50 and they are great amps and if you are a skilled builder they are top-notch. From what I read the HFpacker is a updated/upgraded version of the WA2EBY design. I wanted a low cost option that didn't have or need a bunch of add-ons its just a simple cor keyed amp with pretty low current draw even in the 12v range. 73 ?David ? N8DAH ? |
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Diver Martin
The biggest problem to adding an amp to the uBitx is the fact that it's using the IRF510's as the output amplifier, and the output power is not consistent.? I've thought about adding my 50W amplifier to the uBitx, but the issue there is that the amplifier only needs 0.7W drive at 40m, and needs 3W drive at 10m.? The uBitx is putting out 7-10W @ 40m, and under 3W at 10m, so a variable attenuator or something would be needed, or a set of attenuation resistors and switches. One option might be to reduce the gain (Increase negative feedback) of the output amplifier using R261/R262 which are pretty large at 200 ohms, and increasing the input drive.? I haven't experimented with this yet though, and they'd probably have to be beefier resistors.? All things in due time, my mod PCB project comes first (it's almost done, will hopefully send out a preliminary design email tonight). On Wed, Jan 10, 2018 at 8:44 AM, Rob N4RMK <N4RMK.tn@...> wrote: I'm a total novice with electronics, so I'm not sure whether I could effectively make this mod.? I'm just thinking that a 50 watt or 100 watt amp would be an awesome addition to the uBitx. --
Martin Held - AE7EU ------------------------------------------------------------------------------- If there aren't any questions, then what is there to learn? |
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M Garza
Here is an idea for the variable input pad control: Since you are probably going to have a rotary switch to select the correct LPF, use a double pole rotary switch.? 1 pole controls the LPF and the other selects the correct input pad.?? Yes, it makes the part count increase, but it is only a few more resistors. Just an idea. Marco - KG5PRT On Wed, Jan 10, 2018 at 10:51 AM, Diver Martin <diver.martin@...> wrote:
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M Garza
I guess it would be more like a 4P switch, 2 for the input pads and 2 for the LPFs. You could also use relays. The switch would just turn on the appropriate relays. Just thinking out loud. Marco - KG5PRT On Wed, Jan 10, 2018 at 11:19 AM, M Garza <mgarza896@...> wrote:
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Seems acceptable to twiddle RV1 (or some sort of mike audio gain) when switching bands, given the $120 price.?
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Though we need a convenient way to indicate how far to twiddle. Adding negative feedback as per post 38817 to the existing uBitx final, then driving that reduced but consistent output into something like the WA2EBY is also a good option. Jerry, KE7ER On Wed, Jan 10, 2018 at 09:24 am, M Garza wrote:
I guess it would be more like a 4P switch, 2 for the input pads and 2 for the LPFs. |
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Vince Vielhaber
They say the EBY amp puts out 40 watts with a 28v supply. What's the current draw on that?
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Vince. On 01/10/2018 10:24 AM, N8DAH wrote:
Only ones I know of are the Hardrock-50, HFpacker and the WA2EBY. All --
Michigan VHF Corp. |
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Rob,
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? ?I can also recommend the WA2EBY linear - it works great with my BITX40v3 using a 7dB pad.? The next linear I'll build is the EB63A from Communication Concepts.? It's been confirmed to work with a number of QRP rigs including various BITXs.? Like the WA2EBY amp, it has an RF-operated keying relay circuit so requires no radio mods. ? ?If you decide on the WA2EBY amp, I suspect you'll find it to be a beginner-friendly project.? It's easy to build and adjust, especially with Leonard, KC0WOX's parts list, source links, and build instructions.? His Mouser project list covers all of the parts.? While a couple of the specific numbers are obsolete, Mouser has plenty of replacements.? When I load the list today, I see that we need an alternative for a 500V mica cap, an SMD cap, and a relay snubber diode. The diode can be any 1N4004 or similar. ? ? ? ? Best, ? ? ?Andy, KG5RKP On Wed, Jan 10, 2018 at 07:13 am, Rob N4RMK wrote:
I hope this isn¡¯t too far off-topic to ask here. ?I¡¯ve looked for an amplifier kit similar to the Bitx radio. ?Does anyone here know of such a kit? ? |
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Vince - on 40 meters the prototype WA2EBY drew about 4A from 28V.
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Both of the original QST articles are here (in English) along with a 100W variant (in German):? Andy On Wed, Jan 10, 2018 at 10:46 am, Vince Vielhaber wrote: They say the EBY amp puts out 40 watts with a 28v supply. What's the |
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Vince Vielhaber
Another option would be ALC like on commercially made rigs.
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Vince. On 01/10/2018 11:51 AM, Diver Martin wrote:
The biggest problem to adding an amp to the uBitx is the fact that it's --
Michigan VHF Corp. |
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Or maybe steal some ideas about how to drive the uBitx IRF510 gates from WA2EBY:
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? ??/g/BITX20/message/35508 On Wed, Jan 10, 2018 at 12:38 pm, Vince Vielhaber wrote:
Another option would be ALC like on commercially made rigs. |
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M Garza
Has anyone built the FARA Amplifier?? Any thoughts on it?? It uses a pair of 2SC2312 bipolar transistors. Here is a link for a pdf:? I have a few HG 2SC2312s, so I am debating on ordering a couple of the board sets from FAR Circuits.? ?$18 for the 2 board set. Marco - KG5PRT On Wed, Jan 10, 2018 at 2:18 PM, kc0wox Leeper <kc0wox@...> wrote: You can see a youtube video testing the wa2eby amplifier lowpass filter frequency response at It uses a HP8407a network analyzer to check the frequency response. The first part of the video explains how a network analyzer works and then tests the lowpass filters. |
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Vince Vielhaber
Thanks! That German project is interesting too.
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Vince. On 01/10/2018 02:32 PM, AndyH wrote:
Vince - on 40 meters the prototype WA2EBY drew about 4A from 28V. --
Michigan VHF Corp. |
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The 2SC2312 is long out of manufacture so any "new" ones that you find on ebay will most likely be factory sweepings that were relabled. While it's possible to stress test each and every one that you purchase, there won't be a reliable run to be found. ? But if you enjoy the thrill of finding a suitable substitute, I don't see anything wrong with the design. It's simple and straightforward. You have to be careful not to overdrive it, however as it will probably fry those finals in a very short time. Also, the max ratings on the transistor are about 17 watts each, so if you're driving a pair at 40 watts, you're going to be pushing them a bit. Sent from Yahoo Mail. On Wednesday, January 10, 2018 3:53 PM, M Garza <mgarza896@...> wrote: Has anyone built the FARA Amplifier?? Any thoughts on it?? It uses a pair of 2SC2312 bipolar transistors. Here is a link for a pdf:? I have a few HG 2SC2312s, so I am debating on ordering a couple of the board sets from FAR Circuits.? ?$18 for the 2 board set. Marco - KG5PRT On Wed, Jan 10, 2018 at 2:18 PM, kc0wox Leeper <kc0wox@...> wrote: You can see a youtube video testing the wa2eby amplifier lowpass filter frequency response at It uses a HP8407a network analyzer to check the frequency response. The first part of the video explains how a network analyzer works and then tests the lowpass filters. |
Rob N4RMK
N8DAH