Topics

Inexpensive eBay Amplifier Kits

Arvo W0VRA
 

Anyone have success or other experience pairing a BITX (B40 or µB) with one of those eBay amplifier kits, like this one?

https://www.ebay.com/itm/2017-DIY-kits-100W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3/282521402337

Lee
 

I've read some reviews on these and it seem the big difference between the $36 100w and the $18 70w is the 100w is on 16v and the 70w is 13.8v.. The heat sink for either is $8.   They both need an low pass filter for the band you use it on.  Some people say they cannot wait to retire.  It is great for the first 2 years but I retired in 2010 so I might just build the 70w version for 20m, my favorite band.  
--
Lee - N9LO  "I Void Warranties"

 

Kees T
 

You pays your money and you takes your chances.

Since I sold 20W+ Amp kits, I bought one of these to try it out and run some tests. The MOSFETs had the ID taken off with a grinder. The amplifier worked the first 4 times we powered it up and "went south" the 5th time with limited output. I did get a refund after working with eBay "for a while". The good thing is that they are improving and I'm glad to see them using the sleeve ferrites over copper tubes for the output transformer (#61 material ?). Question the linearity and if it's Class C (probably OK) or Class AB Linear.....and what the top end compression is. Any of these run better at 24V or 18V but I want a 13.8VDC Amp.

73 Kees K5BCQ   

Paul Galburt - K2AYZ
 

I recently bought one on AliExpress.

https://www.aliexpress.com/snapshot/0.html?spm=a2g0s.9042647.6.2.3da74c4d3qZejW&orderId=91238803849901&productId=32574683152

This one features a built-in LPF, which seems unusual - but really convenient. The provided LPF is for 13.56 MHz, but retuning for a ham band seems fairly simple. I have not had time yet to built this kit, but I have contacted the maker a couple of times and they seem responsive.

That said, I think getting them to provide a different filter will be a long, drawn out process, and not in keeping with a $20 kit. The 13.56 MHz filter is not far from what's needed for 40, 30, or 20 meters, so the provided toroids could likely be used.

73,

Paul K2AYZ

Lee
 

Your link wants us to log in.
--
Lee - N9LO  "I Void Warranties"

 

ajparent1/KB1GMX
 

The existing filter can be used to make one for either 40/30m or 30/20m.  You cannot cover
40 and 20m with the same filter as the 40M harmonics fall in or near 20M.   Of course
external switched filter is easy to do.

The 13.56mhz is generally used for heating and other processes allowed in the ISM band.
Those less than 100W amps are likely used as drivers for KW sized (induction heating
and sputtering).  As a result linearity is not a factor and class B or C is often the case.

Allison

Bob KB1TEK
 

ulf.jagfors@...
 

I ordered this PA and a low pass filter board three month ago. The items have not arrived. During several weeks I have now had email discussion throw ebay with this  trader to either send me a replacement or refund me. That has not worked out. The trader did NOT use any registred postal shipment which makes it impossible to trace the shipment. He did not even had my postal address when we discuss a replacement shipment. My advice. Do not buy anything from traders who do not use registred postal service. Do not use traders who has a US-warning on the PayPal service.
This PA will come without any schematics or essembly instruction something that is common for all DIY item from China. Don´t expect hem to send you any info after shipment. Luckely there are a number of instructions on the net which might help you to assembly this type of constructions. Many PA constructions from China seems to suffer from instability. Some of them use re-used outdated final transistors. They are cheap so you get what you pay for. Check on the net for people who has dealt with the DIY item you intend to buy before order. 
I have instead bought a ready assembled PA fully linear within .5 dB for 1.0-30 MHz- Input 100 mV and output 30-40 class AB SSB from Russia. Check RV3YF WEB site for more info and order instructions. Fast delivery with schematics. You need to add your own heatzink. He also have some interesting  s-meter and SWR display which I intend to add to the uBITX.
Ulf/sm0cgl

Glenn
 

That amp seems to be very similar to this one https://www.ebay.com/itm/Upgrade-45W-SSB-linear-Power-Amplifier-Kits-for-transceiver-Radio-HF-FM-CW-HAM/181893455505?hash=item2a59b1de91
but without the first stage and LPF.

There is some info on this one, if you search around the web. But some of the info is conflicting.  It puts out about 30-35W but like most of these cheap amps, power falls away from 40M up.

glenn
vk3pe

Richie Chambless
 

The 45 watt and 70 watt amps use the IRF530, and I own both. They do work, but not for long at the advertised power. It’s very easy to push too hard on the drive and blow the FETs. The 45 watt version only takes 10 milliwatts of drive to get full power, so it can be connected directly to the BitX 40 T/R relay with a 3 to 6 dB pad (bypassing the PA). You can get about 25 watts out on 13.8 volts. The 70 watt amp needs about 1 to 3 watts of drive to work, but can produce 40 to 50 watts from 80 to 20 meters. The output falls off sharply after that. Either way, but some extra IRF530s... you will need them!

Howard Fidel
 

I built the 70 watt model. I changed the 2 IRF530s to 4 IRF520s. The IRF530s oscillated and failed quickly. They also run very hot. The IRF520s run much cooler (2x as many junctions) and are stable putting out 50 watts on 20 meters. The output on 15 and 10 is less, but the uBitx puts out less on those frequencies. I am working on getting it working on all bands, but for now I just use it on 20.

Howard

On 7/11/2018 8:42 PM, Richie Chambless wrote:
The 45 watt and 70 watt amps use the IRF530, and I own both. They do work, but not for long at the advertised power. It’s very easy to push too hard on the drive and blow the FETs. The 45 watt version only takes 10 milliwatts of drive to get full power, so it can be connected directly to the BitX 40 T/R relay with a 3 to 6 dB pad (bypassing the PA). You can get about 25 watts out on 13.8 volts. The 70 watt amp needs about 1 to 3 watts of drive to work, but can produce 40 to 50 watts from 80 to 20 meters. The output falls off sharply after that. Either way, but some extra IRF530s... you will need them!


ulf.jagfors@...
 

I just received info that ebay will pay back all money as the trader had not provided any postal tracking number. Warning for the trader named kiss_buy. He seems to be on all major shopping sites.If a trader do not provide you with a registred postal number cancel the order by return. Inform the shopping site and if used PayPal accordingly.

 

Just my 2 cents. After getting two versions of the "cheapbay" amp I can say the best thing I did. Bought a proper kit like a WA2EBY and built it.The Hardrock 50 was also a great amp but the cost is pretty high. I have not used a HFpacker but know a few qrp guys that swear by them as well.

If you really want 100W look at the HLA-150. I have had much better luck with building a known kit then trying to save a few bones on the cheaper kits with next to no info on them.

In any event best of luck.
--
David

 N8DAH
Kit-Projects.com

Michael P. Rioux
 

I’ve built two of the Hardrock 50’s. They are great amps and pretty bullet proof. I’ve used them on several trips outside
the USA and they’ve done a great job of getting my KX-3’s signal out.
I expect it will do the same for my uBitX if I ever decide on what display and cabinet to use…..
Complete integration between the Hardrock and the ubitX should be doable the same as between the Hardrock and the KX-3.
Too many projects, too little time.

73, Mike W1USN


On Jul 12, 2018, at 12:08 AM, N8DAH <Dherron@...> wrote:

Just my 2 cents. After getting two versions of the "cheapbay" amp I can say the best thing I did. Bought a proper kit like a WA2EBY and built it.The Hardrock 50 was also a great amp but the cost is pretty high. I have not used a HFpacker but know a few qrp guys that swear by them as well.

If you really want 100W look at the HLA-150. I have had much better luck with building a known kit then trying to save a few bones on the cheaper kits with next to no info on them.

In any event best of luck.
--
David

 N8DAH
Kit-Projects.com


4Z1NT
 

Here is a comprehensive build of the cheapo Chinese amplifier with a circuit diagram and confirmation that it works too!!

http://pa-11019.blogspot.com/2016/11/diy-kits-70w-ssb-linear-hf-power.html



On 12 July 2018 at 07:32, Michael P. Rioux <mike@...> wrote:
I’ve built two of the Hardrock 50’s. They are great amps and pretty bullet proof. I’ve used them on several trips outside
the USA and they’ve done a great job of getting my KX-3’s signal out.
I expect it will do the same for my uBitX if I ever decide on what display and cabinet to use…..
Complete integration between the Hardrock and the ubitX should be doable the same as between the Hardrock and the KX-3.
Too many projects, too little time.

73, Mike W1USN


On Jul 12, 2018, at 12:08 AM, N8DAH <Dherron@...> wrote:

Just my 2 cents. After getting two versions of the "cheapbay" amp I can say the best thing I did. Bought a proper kit like a WA2EBY and built it.The Hardrock 50 was also a great amp but the cost is pretty high. I have not used a HFpacker but know a few qrp guys that swear by them as well.

If you really want 100W look at the HLA-150. I have had much better luck with building a known kit then trying to save a few bones on the cheaper kits with next to no info on them.

In any event best of luck.
--
David

 N8DAH
Kit-Projects.com



Lee
 

I have seen some of these come with 30mhz LP filters and some order the model without a filter and add one for the band they will be using.  Is either idea acceptable or is one better than the other.   I just ordered a 70 watt, heat sink, and case on eBay and will have to get a filter. Thank you.
--
Lee - N9LO  "I Void Warranties"

 

Jerry Gaffke
 

Any amateur amp should be followed by a low pass filter suitable for knocking out the second harmonic and beyond.
That means separate filters for 160m, 80m, 40m, 20m, 10m.
You may piggyback some of the other non-harmonic bands into that set of filters,
but that makes the filters much more difficult to design and build.

A rig with only a 30mhz LP filter is likely aimed mostly at CB'rs.

QRP is good for experimenting.
But with a 50W+ ebay amp, you really should be testing for compliance with FCC regs.
It likely fails, and all the nasties will scale up with the output power.

Jerry


On Thu, Jul 19, 2018 at 06:12 PM, Lee wrote:
I have seen some of these come with 30mhz LP filters and some order the model without a filter and add one for the band they will be using.  Is either idea acceptable or is one better than the other.   I just ordered a 70 watt, heat sink, and case on eBay and will have to get a filter. Thank you.
--
Lee - N9LO  "I Void Warranties"

 

Mike aka KC2WVB <rb5363@...>
 

I ordered the $12 tuner kit from the same supplier as these 70 watt/100 watt amps being discussed. I considered the $18 amp but took a pass because too many other chores to do. I am glad I did take a pass. I say this because indeed as commented elsewhere this company gives you absolutely no schematic for the build. Glad I bought just a tuner because that is simple to construct minus plans. The amp would have been a PIA without a schematic. On the other hand it did arrive fairly soon, about 2-3 weeks and the parts are pretty decent.


On Wed, Jul 11, 2018, 6:42 PM <ulf.jagfors@...> wrote:
I ordered this PA and a low pass filter board three month ago. The items have not arrived. During several weeks I have now had email discussion throw ebay with this  trader to either send me a replacement or refund me. That has not worked out. The trader did NOT use any registred postal shipment which makes it impossible to trace the shipment. He did not even had my postal address when we discuss a replacement shipment. My advice. Do not buy anything from traders who do not use registred postal service. Do not use traders who has a US-warning on the PayPal service.
This PA will come without any schematics or essembly instruction something that is common for all DIY item from China. Don´t expect hem to send you any info after shipment. Luckely there are a number of instructions on the net which might help you to assembly this type of constructions. Many PA constructions from China seems to suffer from instability. Some of them use re-used outdated final transistors. They are cheap so you get what you pay for. Check on the net for people who has dealt with the DIY item you intend to buy before order. 
I have instead bought a ready assembled PA fully linear within .5 dB for 1.0-30 MHz- Input 100 mV and output 30-40 class AB SSB from Russia. Check RV3YF WEB site for more info and order instructions. Fast delivery with schematics. You need to add your own heatzink. He also have some interesting  s-meter and SWR display which I intend to add to the uBITX.
Ulf/sm0cgl

Andrew Kasurak
 

wcurlew@juno.com
 

Do you happen to have a source/part number for the heat sink?

Thanks.

Bill KC1JTS