Useful information
for FT817 users ##(關於FT-817有用的資料,i.e 5W 升至10W+輸出)##
Output power
modification
MM0BFF posted a
message on www.mods.dk on 13.7.2002 about a
modification to increase the output power of this rig to 15 watt.
I discussed with him who agreed with me that a 10-watt output for
FT817 is safer based on the specifications of the final MOSFET.
Read MM0BFF's message on 31.7.2002.
| Yaesu
FT817 blown finals and 10 watt modifications##(FT-817升至10W輸出後與末級功率器損壞
)## 15 Oct.2002 updated information de VR2XMC Hi OM, This topic is very hot in the world wide FT817 discussion groups. I think we have to strike the balance of getting 10 watt output and risk of blown finals. Increasing the output power is definitely not an original design parameter. Otherwise, Yaesu should promote the rig as 10 watt output and sell for higher price. Based on this rationale, I keep the variations to the orignial values in the hidden menu #18-53 as few as possible. My rig is the Lot 58 production and my observations are: 1.The gain of the finals at VHF and UHF regions is well less than that in HF region so that there is not much room for increased output. For example, the difference between 7 watt output and the original 5 watt is merely 1.46 dB. Therefore, why border to make any variations to the original values. 2.For HF and 50Mhz, an increased output to around 10 watt can be obtained by simply only changed the values at #24,28,32 and #36 i.e. HF1-HI, HF2-HI, HF3-HI and 50M-HI. Therefore, the changes to the original design parameter are kept to minimal. In other words, there is no change in values for the parameters such as overcurrent protection and TX gain. Although in some bands, you may only get an output of 8-9 watt, the on-air difference is minimal. 3.Once you make the modifications, I would strongly suggest you strictly limit your operation to light duty cycle mode such as SSB when running 10 watt. 4.The theoretical absolute maximum power the pair of finals is 8 watt x 2. Therefore, there is no way you should aim at running the rig at 15 watt !!!! The above is my own observation to my rig. Please don't hold me liable for any damage to your rigs. Good luck! 73 Johnny Siu VR2XMC |
Speech
compressor##(話音壓縮器,i.e增加SSB發射有效功率)##
Talk
power is extremely important for QRP rig. One of the major
shortcomings of FT817 is NO internal speech compressor. There are
commercial alternatives provided by www.box73.com , www.w4rt.com and www.tentec.com
455KHz
IF filter##(455KHz中頻濾波器,i.e加強收及發效能)##
It is a
MUST option for this rig. This filter not only enhances RX
selectivity but also the TX average talk power. It is used both
in the RX and TX path. The stocked Murata filter has a shape
factor fast worse than the option. If you don't like Yaesu
filter, you can get alternatives from INRAD www.qth.net/inrad.
Portable
Antenna##(便攜天線,i.e方便隨時QRV)##
There
are a lot of choices. Please visit www.hamstick.com, www.buddipole.com
Portable
linear amplifier##(便攜功率放大器,i.e方便隨時QRO)##
Apart
from
FT817
Mail reflector##(FT-817討論區, i.e交流、討論FT-817相關資料)##
There
are discussion groups in yahoo, please search www.yahoo.com These groups are
FT817 userswith good
knowledge of the rig.
Manufacture
Bugs
For lot
32 or earlier, there are manufacture bugs in FT817. There is a
strong birdie on 7240Khz.
Pairing
of IF filters##(中頻濾波器配對)##
I have
been approached by hams about the rationale of the filter upgrade
mentioned in www.qsl.net/icom/ic756/fl44a.html
The
details are now given in the website www.qsl.net/icom about the Paired
filters in ICOM Radio.
Fan kits
for ICOM IC781 and ICR9000##(IC781及ICR9000加裝散熱煽套件)##
The main
drawback of IC781 is the substantial heat generated from the
power supply unit. Many IC781s were fatal in this regard and NATO
(north Atlantic theory organization) version of IC781 made
modification to the rig. The modification kit is now available in
USA. Again, please visit www.qsl.net/icom and 'click' the
'IC781 modification kit'
ICOM IC756
IF Filter upgrade##(改進ICOM IC756
中頻濾波器)##
Please
visit www.qsl.net/icom/ic756/fl44a.html
*Thanks for VR2XMC for the above useful information.*
*多謝VR2XMC提供上列有用的資料*