RM Italy KL 503 HD (High Drive)

[trx680]

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Our sponsor here has an amp that caught my eye.
Reason why is it can handle more input. I have a Bearcat 980SSB w/ Astatic Road Devil power mic, with a high performance tuneup that may be putting out at much as 5.5 watts AM and 19 watts SSB (according to my MFJ-849 watt meter). And I read where some recommend having lower input when using an amp, some don't think its really important.

Anyway, this particular amp is their RM Italy KL 503 HD (High Drive) 300W Mobile Linear Amplifier (20-30 mhz). It can handle much higher input: Input power - 1 - 35 W on all modes.
2nd thing I like about it is that it has a variable output, up to 300W. Last thing I want to do is bleed over on other frequencies because I'm always pushing 300W all the time. Got enough of that going on around my way. If I need a little extra push I'll use just what I need.

Here are the specs. Please let me know if something stands out as being "unfavorable":
Frequency - 25-30 MHz
Input energy/power - 12-14 A
Input power - 1 - 35 W on all modes
Output power - 300 W Max
Max Bypass power (Amplifier off): 50W Max
Mode - AM-FM-SSB-CW data etc (all narrowband mode)
Fuse - 3x10 A
Preamp - 26 dB
Input VSWR: 1.1 - 1.5:1
output VSWR max: 2.5:1
Output power level - 6
Electronic switch
Inversion polarity protection
Size - 170x295x62 m

[trx680]

And a few questions:
-Max Bypass power (Amplifier off): 50W Max - So I can have the power off on this and still use my radio and achieve the 5.5 watts AM from my radio?
-Going to need at least a 14 amp power supply? Although I have a 30 amp that will be dedicated to the amp.
- Remember, this is coming from someone who knows nothing about Amps.... what is the "pre-amp" switch all about?

[Blue Ox2]

There are folks that know far more than me but that is a good amp.
I use the 503 and it is on a Megawatt power supply.

The preamp is for receive and can bring the distant stations in better.

JM2 cents,

73,

Mike

[295 antenna]

I also use a RM Italy 503 with a dedicated S-700-12 megawatt power supply. Wonderful amp and i use the bigger power supply because i want more head room when it come to amp draw

[MDYoungblood]

And a few questions:
-Max Bypass power (Amplifier off): 50W Max - So I can have the power off on this and still use my radio and achieve the 5.5 watts AM from my radio?
-Going to need at least a 14 amp power supply? Although I have a 30 amp that will be dedicated to the amp.
- Remember, this is coming from someone who knows nothing about Amps.... what is the "pre-amp" switch all about?

The reason they give a "Max" is to keep you from burning up the contacts in the relays when off. A 30A PS will do just fine, I like a little breathing room on my PS's so as not to stress them. I think that amp would be a good choice for you.
Remember the antenna system has to be able to handle the extra load of the amplifier. and like always the SWR needs to be low as possible.

3's

Greg

[trx680]

And a few questions:
-Max Bypass power (Amplifier off): 50W Max - So I can have the power off on this and still use my radio and achieve the 5.5 watts AM from my radio?
-Going to need at least a 14 amp power supply? Although I have a 30 amp that will be dedicated to the amp.
- Remember, this is coming from someone who knows nothing about Amps.... what is the "pre-amp" switch all about?

The reason they give a "Max" is to keep you from burning up the contacts in the relays when off. A 30A PS will do just fine, I like a little breathing room on my PS's so as not to stress them. I think that amp would be a good choice for you.
Remember the antenna system has to be able to handle the extra load of the amplifier. and like always the SWR needs to be low as possible.

3's

Greg

The Rig Expert is telling me the SWR on am-19 is 1.06. And sideband is 1.26.
I've read where your SWR is more important when using an amp. Hopefully this is good enough.
The antenna is the Maco v5/8 which can handle 1200w.

[nk14zp]

That SWR should be fine. I think a high drive amp is a great choice for your first amp. Now don't get all upset if it doesn't put out max power with your radio. It will last and sound great with a lower powered radio. Remember it's not just watts that get you heard.

[trx680]

got it on order

you guys be listening for me

[Turk182]

Roger that nk14zp-I'm running an RM-KL505 through LM-400 coax to a 10m beam 55' up driven by a stock Galaxy DX-959 turned less than half way up on the "RF Power" dial and still getting near max output on the resonant freq. (A Silver Eagle does help). With a 300w tuner keeping SWR flat, i'd rather run it to 250w peak and make it last. That last 50w won't make a diff. anyway.

[trx680]

Roger that nk14zp-I'm running an RM-KL505 through LM-400 coax to a 10m beam 55' up driven by a stock Galaxy DX-959 turned less than half way up on the "RF Power" dial and still getting near max output on the resonant freq. (A Silver Eagle does help). With a 300w tuner keeping SWR flat, i'd rather run it to 250w peak and make it last. That last 50w won't make a diff. anyway.

Tell us more about your tuner.

[2ndString]

Do the rm Italy amps need to be converted to run 11 meter or are they ready to go CB out of the box?

[Deleted User 30222]

Do the rm Italy amps need to be converted to run 11 meter or are they ready to go CB out of the box?

It is ready to go. I run a KL503 myself using a Megawatt S-350 power supply.

[2ndString]

Very cool and good to know. I was in a CB shop that told me they had to be converted. He had some mark up, which is expected. They have to make a profit. The information he was giving was confusing though.

[MDYoungblood]

Very cool and good to know. I was in a CB shop that told me they had to be converted. He had some mark up, which is expected. They have to make a profit. The information he was giving was confusing though.

The only mod he could possibly do is get you to open your wallet, , the amp is already setup for 20 to 30mhz. Sounds to me like a place I wouldn't go back too.

3's

Greg

[TheBohunk]

Been reading up a lot on this amp and Amps in general. Seems like the general consensus drive them with as few watts as possible.

But I’m curious if this thing would survive at 4 or 5 watts seeing as how it is supposed to be a high drive amp with a much higher input rating?

My Galaxy base I can turn down but the old Midland in the truck I can’t. I was kind of thinking of picking up an amp that would work in both in case I wanted to upgrade the base at a later date.

If the 503 won’t survive behind The Midland, is there another affordable amp for a beginner that will?

[Turk182]

Roger that nk14zp-I'm running an RM-KL505 through LM-400 coax to a 10m beam 55' up driven by a stock Galaxy DX-959 turned less than half way up on the "RF Power" dial and still getting near max output on the resonant freq. (A Silver Eagle does help). With a 300w tuner keeping SWR flat, i'd rather run it to 250w peak and make it last. That last 50w won't make a diff. anyway.

Tell us more about your tuner.

My MFJ-949E-handles about 300w, but I always make sure I'm coming in under that. I like this one, since it has a built-in dummy load, two-coax capable, tuned and bypass switch, and a nice big readable meter for my tired, 56 yr. old eyes. I may eventually graduate to a Palstar AT2K if I decide I need a bigger heater.

[edfiero]

Bumping up this old thread. I was thinkin about one of these amps. Hoping to drive it with about 30 watts. Will it hold up?

[Blue Ox2]

Hi edfiero,

Actually, the RM KL 503 runs better on a MegaWatt S 400-12.

I use one all the time.

73,

Mike

[Super60]

I was planning on getting a KL-503 but they are out of stock everywhere and for all I know out of production as it may be superseded by the kl-503HD ,I don't know. My question is simple ,can my out of the box factory President McKinley work satisfactorily with the 503 HD or would the old 503 be better? Thanks

[295 antenna]

I got a new 503hd and i needed at least 25 watts to get decent power out of it so i believe my old 503 worked the best with a stock radio.

[Super60]

Thanks for the reply That is sort of what I figured.

[Blue Ox2]

I have the 503 HD and run it through the 142 GTL that is direct injected, and all. Works fairly well from what the guys down yonder report to me.

I have it wired to run through the McKinley as well. Works well on low power for me.

73,

[Super60]

Thanks for your reply. So we have now one that needs 25 watts pep to make the HD work well and the other says his works well with a stock McKinley. My Mckinley PEP in SSB according to my MDS meter says around 12 to 13 watts.
Well I don't know whether to wait for the possibility of the kl-503 [non HD] to come back in stock or opt for the HD. I did ask 88Radio if and when they were to be back in stock quite awhile ago and haven't heard back and most likely never will. Could I run my Mckinley into my kl 203 and then into a HD with the Mckinley output turned all the way down?? A long shot I would think that most likely wouldn't work and blow the HD.

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[MDYoungblood]

There isn't a lot of difference between to older model and the newer, a modest 12w's will drive it rather nicely, it is just built a little tougher because of the high power radios on the market. It won't drive up to maximum wattage but the life expectancy will be a lot longer.

3's

Greg

[Super60]

Well that's encouraging ,thanks for your input. Maybe I'll just get one. At present at my base I run a horizontal Dipole with my Mckinley and a small KL-203.