Topics

Which band for your SB2? #poll

Lincoln Thormahlen
 

Just what the title says, which band will you be building your SB2 for? supplied 20m or 40m?  or other band?

Lincoln
N9IN

 

#118 is 40m

On 2/12/2019 2:34 PM, Lincoln Thormahlen via Groups.Io wrote:
Just what the title says, which band will you be building your SB2 for? supplied 20m or 40m?  or other band?

Lincoln
N9IN

ajparent1/kb1gmx
 

#117 is set for 40m.

Allison

W3DX
 

#111 20 meters. I’m a 20 meter man all the way. W3DX

Gil
 

dl2arl@...
 

...what about other bands? Like 17m? This one should go with the parts ordered, take or leave the one or the other capacitor being too big. Software could be adapted, the Si5351 should work and the intermediateFreq should be far enough.

I have tried to recalculate the transmit filter between the mixer output and the PA chain (transmit band pass filter) and must say, I am not able to understand what I am doing wrong. Simulating the given values for both SlopBucket I and II gives me filter curves I do not recognize as such. I start with an impedance of 450..500Ohms on the mixer side and end up the filter with the 4k7 resistor to ground in the gate of the T2 transistor. I am not using the component values taken from the "Power and Transmitter Section" drawing but those taken from the parts list (band specific).

What am I doing wrong? The filter curve yielding of my simulations resembles to a long dead dromedary camel with two unlike bumps on it's back, none of them even near 20m. Guess it should be something very simple I am missing. This is why I am asking so shy.

And now, that I have your attention, there is another point I need assistance. So far I built the first version. There was a bipolar capacitor C 68 intended to be 10uF parallel to R48 in the gate of Q13 doing the AGC. Well... I took my hat off and held the capacitor for a silent moment in my hand. I am of an older semester and must confess, I never ever have seen so much of a capacity in a such a small case. Incredible!
I was so impressed, I forgot to measure the capacitor to see with my own eyes what my mind could not believe. Did anybody do measure that cap? Incredible as I said.

Yours friendly, Razvan DL2ARL

Don, ND6T
 

75M for #144.  And I think that I have just the case for it!
73,
Don

Dale Lam
 

I'm building my SB2 s/n 146 for 40 meters.

Dale Lam - N0OU - Kansas City, MO

Steven Weber
 

If you think the 20M filter models weird, the 40M filter looks really bad. But it works. I tried to minimize the number of different values needed to kit, so it’s not quite optimum.

 

Two things. The output of the SA612 is more like 1.5K, which is the figure I use for the input. The jfet on the output of the filter adds 5-7 pfd to the last capacitor value. Using those values, the filter still has a little peak on either end, but is reasonably flat. You can’t really make a flat response with this topology. To do that it really requires using a high pass and low pass filter in series, which uses more parts and takes up more space and is more difficult to get steep sides without using a lot of poles.

 

Yes, C68 really is a 10 ufd cap. I’ve seen them as big as 47 ufd, they get pretty big at that capacity.

 

73, Steve KD1JV

 

 

...what about other bands? Like 17m? This one should go with the parts ordered, take or leave the one or the other capacitor being too big. Software could be adapted, the Si5351 should work and the intermediateFreq should be far enough.

I have tried to recalculate the transmit filter between the mixer output and the PA chain (transmit band pass filter) and must say, I am not able to understand what I am doing wrong. Simulating the given values for both SlopBucket I and II gives me filter curves I do not recognize as such. I start with an impedance of 450..500Ohms on the mixer side and end up the filter with the 4k7 resistor to ground in the gate of the T2 transistor. I am not using the component values taken from the "Power and Transmitter Section" drawing but those taken from the parts list (band specific).

What am I doing wrong? The filter curve yielding of my simulations resembles to a long dead dromedary camel with two unlike bumps on it's back, none of them even near 20m. Guess it should be something very simple I am missing. This is why I am asking so shy.

And now, that I have your attention, there is another point I need assistance. So far I built the first version. There was a bipolar capacitor C 68 intended to be 10uF parallel to R48 in the gate of Q13 doing the AGC. Well... I took my hat off and held the capacitor for a silent moment in my hand. I am of an older semester and must confess, I never ever have seen so much of a capacity in a such a small case. Incredible!
I was so impressed, I forgot to measure the capacitor to see with my own eyes what my mind could not believe. Did anybody do measure that cap? Incredible as I said.

Yours friendly, Razvan DL2ARL

_._,_._,_

 

dl2arl@...
 

Thank you Sir, thank you dear Friend for the quick and answer that gives me the clue I was asking for. This makes things little easier in my prospect of moving the SB to 17m.

ohwenzelph
 

It’s waiting for me, so I’d o not know the sn yet but the first one was built for 20 so the plan for #II is 40
aa1of

John AE5X
 

20m for mine and nearing completion.

John AE5X
https://ae5x.blogspot.com/