HF projects

ICOM IC-7200

Vertical stack-up for portability and to reduce base station footprint:

A 1/4" plastic sheet is bolted to the mobile mounting bracket providing a platform in which to attach the LDG IT-100 tuner, Elecraft W2 watt / SWR meter and sensor.  LED accent lighting strip underneath the plastic platform provides lighting for the IC-7200 front panel buttons in low ambient light conditions.

Click on the image below to watch an 8 second looping GIF animation showing daytime (4 seconds) and nighttime lighting (4 seconds).

Yaesu FT-857D

MH-59A8J DTMF microphone modification (W1AEX) - for improved low-end frequency response:

W1AEX original proposed modification (PDF) for improving low-end frequency response (reposted here with permission from W1AEX).

Components bridged (labeled V334, A475, D104) with 1uF Tantalum capacitors.  Not shown is enlarged microphone port opening, and internal baffle removal.  Yaesu FT-857 mic gain set to 15 (of 100) after a VHF audio test with other local hams. W1AEX recommends a setting of 20.

PSK31 PC soundcard interface cable for Yaesu FT-857D / LDG YT-100 tuner:

Yaesu FT-857D data to PC interface cable simple, non-isolated audio design: schematic (PDF), gEDA/gschem file (Linux)

[This circuit seems to be noisy (birdie heard) when the FT-857D frequency is adjusted every second by gpredict software for satellite doppler shift tracking, but no switching noise is heard when changing frequency with fldigi software - laptop or grounding issue? Maybe a Yaesu CT-62 cable will work better.]

Another proposed Yaesu interface cable:

PSK31 receive-only interface cable for Yaesu FT-857 / Lenovo X61 laptop:

No isolation - beware of ground loops!

LDG YT-100 tuner/radio interface cable 8-pin mini-DIN insertion force issue:

The LDG supplied 14" cable which has sharp-edged, rectangular ended pins on the 8-pin mini-DIN makes it difficult to insert this cable into either the LDG YT-100 tuner or Yaesu FT-857 CAT port. A Sun Microsystems 6' keyboard extension cable (P/N 530-1442-02) has slimmer, round-ended pins for easier insertion - and hopefully has less wear on the radio or tuner CAT connectors. This cable is shielded, fully pinned, straight through, for compatible tuner operation with the radio!

Antenna experiments

HF whip antenna PVC stand (using clamp mount):

Counterpoise or radials required.

Inverted-V antenna (using MFJ-1620T 20 meter "HF Stick"s, reused from a MFJ-2220 kit):

Homemade aluminum V-bracket

[This design had tuning and SWR issues - maybe should try reconfiguring for V orientation (need counterweights), instead of inverted-V.]

Venetian blind headrail HF indoor antenna (patio door aluminum frame as counterpoise):

A wacky idea that really shouldn't be published!  The result of my early foray into HF.

SWR is approximately 4.4:1 on 20 meters, and 2.3:1 on 10 meters - as measured with Autek Research VA1 analyzer. This antenna setup is probably best suited for 10 meters, where the background S-meter noise is the lowest. FYI: venetian blind headrail is 8 1/2' long, and patio door is 8' wide x 6 1/2' tall.

CQWW DX contest 20m contact (w/venetian blind antenna)

With this antenna, I made a CQWW DX contest contact from my home QTH in Silicon Valley to VE3EJ in Grassie, ON, Canada with 20 watts on 20m, 14.24650 Mhz @ 23:15 UTC 10/25/2009.

Yaesu FT-857, LDG YT-100, (w/o Radio Works T-4). SWR is 4.4:1, as measured with Autek Research VA-1, where the LDG YT-100 tuner was originally connected.

Contraption installed using sliding window lock attached to patio door frame, and coax center conductor clip attached to venetian blind headrail.

Miscellaneous

HF RFI from 120VAC LED lamp:

S-meter noise reading indicating HF RFI from 120V LED lamp, as picked up by indoor 15 meter Isotron antenna located 12 feet away - whereas incandescent light bulbs do not have this problem. [Note: have not re-investigated the issue using my 15m Dunestar filter.]