final transitor defekt

[Olli]

 Hi what alternatives are there for the final transistors of hermes lit 2 bord

Digikey no longer has them

[Clifford Heath]

Digikey claims that AFT05MS004NT1 is a substitute and that is still available, though NRND.

The schematic also says it’s possible to mount a TO-220 transistor, dissipating heat to the case, but I didn’t search for suitable ones.

Clifford Heath.

> On 13 Sep 2025, at 9:39 pm, Olli <kudalsk...@gmail.com> wrote:
>
> Hi what alternatives are there for the final transistors of hermes lit 2 bord
> Digikey no longer has them
>

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[Olli]

I think the transistor is not the right one. According to digikey it is for uhf and vhf and not for shortwave

[Juergen Hussels]

And VHF fets stop working when they are seeing RF only? :-) Actually many PAs usw VHF / UHF fets. 

The side effects might be higher amplification and perhaps tending to oscillate. But this ist probably not happening, as the layout is good.

Regards,

Juergen DL4JY

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[Olli]

Is there no decent replacement type

[Clifford Heath]

On 14 Sep 2025, at 8:30 pm, Olli <kudalsk...@gmail.com> wrote:
>
>
> Is there no decent replacement type

The AFT05MS004NT1 is the right replacement. It has a slightly lower power rating, so turn the bias down slightly perhaps.

The original AFT05MS003 is characterised 1.8-940MHz, but that doesn’t matter. Both these transistors work down to DC. It’s not like MMICs with internal bias management that often doesn’t work down below the frequency of the bias loop.

The data sheet of both transistors says "Unmatched Input and Output Allowing Wide Frequency Range Utilization”. It’s just that the newer device isn’t characterised for usage at HF. Regardless of that, they’re nearly identical devices.

Clifford Heath.

> To view this discussion visit https://groups.google.com/d/msgid/hermes-lite/8fe5bf4d-7edd-4afb-8f97-fdbe4bcd5308n%40googlegroups.com.

[Olli]

Okay, I'll order some. What I'm still looking for is the program to adjust the bias. I'm looking for the Hermes-Lite 2 test and setup utility.
Where else can I find that?

[Doug Holsted]

Thanks, I have the same question.

[Steve Haynal]

Hi All,

If you are replacing a LDMOS device on a a HL2 from the past few years, then the AFT05MS004NT1 is what was used. If you are building something on your own, then review the posts in this group related to the LDMOS devices as some other component values were changed with the switch to the AFT05MS004NT1. Use the GUI interface to search:

https://groups.google.com/g/hermes-lite/search?q=AFT05MS004NT1

https://groups.google.com/g/hermes-lite/search?q=AFT05MS004

https://groups.google.com/g/hermes-lite/search?q=AFT05MS003

73,

Steve

kf7o

[Clifford Heath]

I think this is the relevant message:

<https://groups.google.com/g/hermes-lite/c/aKoqQCjjXNs/m/KBVrEe3VAAAJ>
"Changing R92 and R99 from 270 to 220 Ohms lowers the gain a bit. “

Clifford Heath.

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