Project 'YASSA-2' - Yet Another Solid State Amplifier (#2)

February 2025: This amplifier is an experiment with the ART2K5TFUS LDMOS FET to produce a compact 6m amplifier that will pair with my IC-705 ... both as a 'second 6m station' at home, and in a '6m DXpedition package'.

My experience with LDMOS RF amplifiers shows that running a device at less than 80% of it's Vdd rating provides a rugged amplifier capable of withstanding 'accidents' like antenna faults or connector failure without requiring protection systems (I'm a big fan of the 'minimalist' and 'KISS' principles!)   So, while the ART2K5TFUS is a 75V device, it will be run at about 50V and 1000W for exceptional safety and reliability ... valuable attributes in a portable PA.

In addition, this amplifier will be made smaller and lighter than my previous 6m portable PA. The heat sink chosen from my junk box is only 200mm x 160mm x 40mm (8" x 6.3" x 1.6") to keep the amplifier's overall size and weight down.   To compensate, two high volume air fans will assist with the cooling.

Neither of the recycled heat sink or copper heat spreader were flat/true, so a helpful local Ham with a milling machine resurfaced both ...




Late February 2025:   Progress on the electronics side of this project is halted for the moment due to a package of components held up in NZ Customs due to incomplete/inaccurate export/import documentation by DigiKey which has resulted in double taxation plus other extra unnecessary fees. So far DigiKey have not responded to emails regarding this issue.

Update 1:   DigiKey responded a week later but did not accept responsibility for their error or offer a viable solution. Their offer was vague and lacked detail (I think it says 'a partial refund as a credit' ??) Now they are not replying to my reasonable questions about how much? or how it would be applied? The issue has been escalated to a dispute and claim via PayPal. More on this shockingly poor customer service by Digi Key will follow ...

Update 2: early March 2025:   The involvement of PayPal dispute got the attention of DigiKey. They acknowledged the issue was their fault and we came to an agreement that I pay the extra charges to release the parcel and they would reimburse me the US$157.84 involved. I did so, and DigiKey issued a 'credit memo' for the amount. So far, after several more weeks and many emails, DigiKey have not reimbursed the money.

Along with up to 1 week delays in email responses, DigiKey has finally claimed that their international payment system is not working, and get this ... "it has not been working since November 2024." So, here is an international company who cannot get its faulty accounts system fixed for 4 months? Really?

Update 3: late April 2025:   Finally, more than 2 months after the initial purchase, DigiKey reimbursed me for the extra expences involved as a result of their incorrect export/import documentation. This reimbursement was made as a simple, straight forward 'refund' via payPal which was always available to them as a payment/refund mechanism that only takes a few minutes to complete. Why DigiKey chose to 'string out the process' for 7 or 8 weeks longer than was necessary is beyond comprehension ... it certainly turned this customer right off dealing with them ever again.

Result:   I'm an avid electronics experimenter making many electronics component purchases each year. There are other component suppliers (e.g. Mouser and Farnell) and I will use them in the future. This whole process was just dumb customer relations by DigiKey which will cost them thousands of dollars in lost sales to me.   Needless to say, DigiKey are NOT recommended!


In the mean time, the metal work continues ...





April 2025 ...









This project is on-going and will be updated here from time to time ...