Re: Problems, now that the radio is completed

Charles W. Powell

Answers below.  This also addresses some of the follow-up questions, so in the interests of not flooding the list, I think Will and Wayne can glean answers from my comments.

On Apr 12, 2018, at 7:54 AM, Dave Benson <davek1swl@...> wrote:


1) Do you recall what frequency first came up when you first went into cal mode? The adjustment range is presently +/- 2.56 kHz. 

It was 14061.61, so within range.  I don’t know what I did to make it work; I simply “tried again” and I made sure I left the power on for about a minute after I was happy with the frequency.  When I powered up again, it was darn close to 14060.

2) The goal is 800 Hz. I assume you mean that the pitch is too high, which means the oscillator frequency is too high.  You should also be able to verify the frequency on another receiver - it should be at approximately 5185.9 kHz.  I'd suggest visually inspecting the capacitor values for that BFO circuit- let me know.

I was not able to get the BFO to match the sidetone frequency, but after I got the LO to the right transmit frequency, the BFO centered on a 600 Hz tone.  This suits me because I find an 800 Hz tone “shrill” and fatiguing.  So I will put up with the side tone being a high pitch.  Hams are generally pretty terrible about zero beating anyway.  I can always use RIT to make it comfortable but nonetheless, if they hit spot on it will be 600 Hz.  I’m good with that.  For some reason, the passband is fine at 600, way down at 700, then comes back up at 800 Hz according to my tests “by ear."

3) The gain control has an adjustment range in the low 30s (in dB). It's there to prevent front-end overload, and also mitigates item 4)

I should be able to determine how well it works when I take it to the field today.  Nice day here.  I’ll see what happens with a signal that isn’t 3” from the radio.

4) Audio screech: I had tried putting limiting diodes in the AF final. As they began conducting on large signals, they significantly detuned the bandpass function. Perhaps the most practical solution replaces the NE5532 with a (DIP) TLV2462. This raises the amp's internal current-limiting threshold from 34 mA (typ) to 80 mA. In simpler terms, that's about 8 dB more audio headroom. 

I took the power down to 1/2 watt on the KX2 I was using for testing.  It did not overload or oscillate with the lower power and the KX2 transmitting into a dummy load.  That tells me that the radio is quite sensitive.  When I get home I will run some tests to see exactly where it starts to “hear."

5) I've been informed it's actually mode B, and confusion over that seems widespread.  It was mode A originally and a firmware revision changed that. This an 'action item' for me- I need to establish a way to choose either one on a one-time basis and retain it in EEPROM- along with the paddle reverse.

Well, the unit I have most assuredly is Curtis mode A.  If there is a way to change it, PLEASE tell me.  I truly cannot send with mode A.  I’ve been using mode B for 35 years and old habits die hard.  If there is an update to the firmware that will allow mode B (or make it the default) I will be a happy camper.

You can keep the rig permanently in Straight Key mode with a monaural plug- left in permanently. It should then 'pass through' the signal from an external keyer.
I don't envision offering it as a menu choice.

I will have to make myself a short adapter for this.  I can force it to start in SK mode by holding the dash paddle, then changing out the key.

PA ruggedness:  I've built three Hilltoppers and at least that many predecessor designs using the 3xBS170 PA scheme. I haven't lost any PAs during boneheaded key-down mishaps. They seem to be pretty rugged. 

Good to know about the PA.  I also won’t worry if the SWR isn’t spot on.  I often use a 1/4 wave vertical, but the ground side is usually pretty random - a few wires on the ground, dangling from a picnic table.  Should be fine in that case.

I will report back after I get out this afternoon.



73- Dave, K1SWL

On Wed, Apr 11, 2018 at 9:30 PM, Charles W. Powell via Groups.Io <doctorcwp@...> wrote:
First, the radio sounds great and it seems to put out at least 5 watts, but there are a few problems I have encountered.

  1. After trying to match the frequency with the Cal jumper in place, the radio is again off frequency after I power cycle it. (about 1.2 KHz high - I can live with that.)
  2. The BFO is about 400 Hz too high (or 600 if the goal is a BFO frequency of 800 Hz.)  My KX2 is set at 600 Hz which appears to be around the peak of the passband on the Hilltopper.  If I try to adjust further, the BFO frequency merely starts to climb higher, and farther away from the desired frequency.  The trimmer cap I think was all the way down tight.  Which way does the trimmer go?  Increase or decrease capacitance?
  3. The gain control doesn't seem to do much.  That may have to do with proximity to the transmitter, but it seems it should do something.
  4. If you overload the front end of the receiver, it throws it into wild oscillation in the ear buds. OUCH!
  5. I am useless with iambic mode A. I simply can't use it after 35 years of iambic mode B and self-completing characters. Is there a way to permanently set the radio for straight key use? (Maybe short the outer ring to ground?)  Because of my other radios I do not have the ring connected (Elecrafts don't like it, except the K2.)
At a minimum, I must get the BFO frequency in the right place to try it in the field.

One more thing - how tolerant is the final to bone headed accidental keying without a load?  Haven't blown anything yet, but not wanting to do so either!

Oh great gurus of the Hilltopper, where should I go first?



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