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L4 and L7 Keying Relay Not Needed....

Jim W7RY
 

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The drake (both the L4 and the L7) use a 22 volt ac transformer winding for the relay shown below is part of the filament transformer, and showing the winding that is used for the PTT relay power supply.

22 VAC X 1.41 (from converting AC to DC) is 31 volts DC.

Most if not all modern radios can easily handle 40 volts DC on their PTT relays and MOSFETs (like the 7610)
In addition of CR5 and R30 shown on the schematic below, also helps to quash any voltage spikes generated by the relay coil collapsing when voltage is removed from it.

So the bottom line... It's not needed.


Let me know if you have questions.

73, Jim W7RY
 

Jim that's good to know. Thank you for that information.

Joe ki5o?
 

When I first hooked up my IC-7610, I measured the voltage on the L7 before connecting and have been using the pair since I bought the 7610 last year. I also checked the rating of the 7610.?Use the FET for keying.?

I currently have switching set up through my C-4 to use the amp with the 7610, plus my B Line and TR7.

Steve Wedge, W1ES/4

Time flies like an arrow. Fruit flies like a banana.


Sent from for iOS


On Tue, Jan 9, 2024 at 8:41 PM, Jim W7RY via groups.io <jimw7ry@...> wrote:


The drake (both the L4 and the L7) use a 22 volt ac transformer winding for the relay shown below is part of the filament transformer, and showing the winding that is used for the PTT relay power supply.

22 VAC X 1.41 (from converting AC to DC) is 31 volts DC.

Most if not all modern radios can easily handle 40 volts DC on their PTT relays and MOSFETs (like the 7610)
In addition of CR5 and R30 shown on the schematic below, also helps to quash any voltage spikes generated by the relay coil collapsing when voltage is removed from it.

So the bottom line... It's not needed.


Let me know if you have questions.

73, Jim W7RY
 

I would toss the silly 1/2 wave rectifier and at least use a FWB? or a FWD, depending on the application.? ?That 22 ohm resistor is not going to do much to speed up the RLS time, it's value is too low for that.? But for the oem 3PDT mech relay, it's good enough? and a moot point.?
Bob KD6GNB
 

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Well hi y’all?
I see the discussion is about Drake HF radios I was directed here ?to look for assistance ?with a Drake UV3?
So once again I will ask can anyone refer me to the correct group?

Thank you
Bob Kd6gnb?


On Jan 10, 2024, at 08:40, Jim VE7RF <jim.thom@...> wrote:

?I would toss the silly 1/2 wave rectifier and at least use a FWB? or a FWD, depending on the application.? ?That 22 ohm resistor is not going to do much to speed up the RLS time, it's value is too low for that.? But for the oem 3PDT mech relay, it's good enough? and a moot point.?

 

Bob, you're in the right place!

Question away!
John

On Wed, Jan 10, 2024 at 1:33?PM Bob KD6GNB <behrhorn@...> wrote:
Well hi y’all?
I see the discussion is about Drake HF radios I was directed here ?to look for assistance ?with a Drake UV3?
So once again I will ask can anyone refer me to the correct group?

Thank you
Bob Kd6gnb?


On Jan 10, 2024, at 08:40, Jim VE7RF <jim.thom@...> wrote:

?I would toss the silly 1/2 wave rectifier and at least use a FWB? or a FWD, depending on the application.? ?That 22 ohm resistor is not going to do much to speed up the RLS time, it's value is too low for that.? But for the oem 3PDT mech relay, it's good enough? and a moot point.?

Jim W7RY
 

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BUT PLEASE start a new email with the proper subject Bob.

Thanks
Jim W7RY


On 1/10/2024 12:35 PM, John K5MO wrote:
Bob, you're in the right place!

Question away!
John

On Wed, Jan 10, 2024 at 1:33?PM Bob KD6GNB <behrhorn@...> wrote:
Well hi y’all?
I see the discussion is about Drake HF radios I was directed here ?to look for assistance ?with a Drake UV3?
So once again I will ask can anyone refer me to the correct group?

Thank you
Bob Kd6gnb?


On Jan 10, 2024, at 08:40, Jim VE7RF <jim.thom@...> wrote:

?I would toss the silly 1/2 wave rectifier and at least use a FWB? or a FWD, depending on the application.? ?That 22 ohm resistor is not going to do much to speed up the RLS time, it's value is too low for that.? But for the oem 3PDT mech relay, it's good enough? and a moot point.?

--
Thanks and 73, Jim W7RY
Rick W4XA
 

There's one thing that maybe should be kept in mind about what people may be using to drive their L-7 or L-4 /L-4B when it comes to ICOM transceivers. ??

I'm not sure that everyone who uses ICOM radios are using the IC-7600/7610 or the even IC-7800/7850/51's? for that matter.

A very large portion of them have the IC-7300 transceiver.? I don't know the actual numbers but it seems A LOT of people I talk to these days are using what one amateur I know calls the "Belly-Button" radio? (everybody has one!)

Directly connecting the IC-7300 to an L-7 or L-4 could eventually damage/destroy the send relay. Hence the "Warning" from the manual.

The below statement is taken directly from the ICOM 7300 instruction manual:
The IC-746, 7410, and others are similar

?WARNING!
??The maximum signal level of the [SEND] jack is 16 V/0.5 A DC. Use an external unit if your non-Icom linear amplifier requires a control voltage and/or current greater than specified.


I also found that my L-4B in stock configuration could not be "keyed" directly with the IC-705 or my IC-M802. Both of which use "open collector" type keying. (For the IC705, I suppose it should probably be called "open? drain" FET keying etc...)

The IC-M802 easily drives the L-4B to 1000W or more output.

Now,? before anyone laughs at? using an IC-705 to drive the L-4B, it's 10W output drives my L-4B to about 250W
(and having said that, I normally use the 705 to drive a Mercury III to about 1200-1300w on 160-40.? It's a little less above ...)

Since my C-line only drives the L-4B to around 1300w, it's a tad over a 7db difference when driving with the IC-705.

But I MUST use a keying interface with both the M802 and 705.

I'm currently using a CRYDOM MPDCD3 (opto-isolated) solid state "relay"? with a pair of 3-vdc series lithium batteries.


Of particular note is the max turn-on/turn-off time of? only 0.1ms .....? There are many other DC (and AC)? controlled solid state "relays" that will control DC and AC and switch with similar times

You could use "accy port -supplied" DC voltage for it.? The IC-705 doesn't have DC voltage available in the "SEND" line so I used the 2x3v battery holder for maximum isolation. (it only draws about 4ma from the batteries during "key-down")

Just another way to do it if desired and it works for just about any amp.


--

73/Rick

W4XA
*Every post is created using Linux

 

Which brings up best practices.? Always check the amplifier keying voltages/currents against the ratings of your exciter.? As shown here, even within a brand with two models that are still in production (7300 vs 7610) you can have entirely different specs.

73,

Steve Wedge, W1ES/4

Time flies like an arrow.? Fruit flies like a banana.

Sent with secure email.

On Wednesday, January 10th, 2024 at 3:08 PM, Rick W4XA <myr748@...> wrote:

There's one thing that maybe should be kept in mind about what people may be using to drive their L-7 or L-4 /L-4B when it comes to ICOM transceivers. ??

I'm not sure that everyone who uses ICOM radios are using the IC-7600/7610 or the even IC-7800/7850/51's? for that matter.

A very large portion of them have the IC-7300 transceiver.? I don't know the actual numbers but it seems A LOT of people I talk to these days are using what one amateur I know calls the "Belly-Button" radio? (everybody has one!)

Directly connecting the IC-7300 to an L-7 or L-4 could eventually damage/destroy the send relay. Hence the "Warning" from the manual.

The below statement is taken directly from the ICOM 7300 instruction manual:
The IC-746, 7410, and others are similar

?WARNING!
??The maximum signal level of the [SEND] jack is 16 V/0.5 A DC. Use an external unit if your non-Icom linear amplifier requires a control voltage and/or current greater than specified.


I also found that my L-4B in stock configuration could not be "keyed" directly with the IC-705 or my IC-M802. Both of which use "open collector" type keying. (For the IC705, I suppose it should probably be called "open? drain" FET keying etc...)

The IC-M802 easily drives the L-4B to 1000W or more output.

Now,? before anyone laughs at? using an IC-705 to drive the L-4B, it's 10W output drives my L-4B to about 250W
(and having said that, I normally use the 705 to drive a Mercury III to about 1200-1300w on 160-40.? It's a little less above ...)

Since my C-line only drives the L-4B to around 1300w, it's a tad over a 7db difference when driving with the IC-705.

But I MUST use a keying interface with both the M802 and 705.

I'm currently using a CRYDOM MPDCD3 (opto-isolated) solid state "relay"? with a pair of 3-vdc series lithium batteries.


Of particular note is the max turn-on/turn-off time of? only 0.1ms .....? There are many other DC (and AC)? controlled solid state "relays" that will control DC and AC and switch with similar times

You could use "accy port -supplied" DC voltage for it.? The IC-705 doesn't have DC voltage available in the "SEND" line so I used the 2x3v battery holder for maximum isolation. (it only draws about 4ma from the batteries during "key-down")

Just another way to do it if desired and it works for just about any amp.


--

73/Rick

W4XA
*Every post is created using Linux

 

You have yet another issue with the L4B / L7. The oem 3pdt mech relay in both amps takes 17 msecs to operate.? Unless the xcvr has a delay circuit, it will hot switch the TR relay in the L4B/L7, like when using VOX SSB / semi break in CW.

My MK-V has a 0-30 msec delay, but only on CW mode. For SSB, I had to use an external delay... which grnds the TX inhibit lead in the yaesu MK-V.? ? ? Same deal on my FT-1000D.??

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