Hello

I do not know if there is a place dedicated to presentations, but I will probably not open another topic and my presentation is about what I am so doing here.
I am French, engineer, 24 years old. Strangely for this forum, I am not amateur radio nor passionate by that. I am passionate about space exploration and especially of Venus. This passion led me to write a 40 pages report on the exploration of the planet's upper atmosphere (report not yet translated into English, but if it interests a francophone, I can send it to you). Today, I think about a "low-cost" mission to this planet and the only point that I can not control is communication to the land without which the mission has no interest. So I would like to have your help to size the system with mass, size, rate , power, order of magnitude of the price. Priorities are in descending order mass, price, ease of use (wide opening angle), rate.

I started the calculations by taking the deep space network as a receiving station but not pushed to full capacity.

Frequency: 9400 MHz => 79db
Distance: between 50 and 260 million km (31 to 160 million miles) => 154 to 168 db
Antenna of reception: 35m (115 feets) of diameter => 68db
Minimum reception power: 10 ^ -17W => -140 db
Antenna resignation: 0.25m (10 inch) => 25 db
After calculation I
Receive power: between 32.5 and 47db => 2 to 48 w (depending on the distance)

Question
1) Is the calculation good?
2) Is this power level possible?
3) What equipment would it take to make it work?
4) What rate could we have?

The problem is that it has an opening angle of 10 , but it will be difficult to point the antenna accurately since there is no reference. So it would be nice to have a wider angle antenna. For this purpose, I saw that the Soviet Vega probes had a balloon that transmitted directly to the Earth with a conical antenna (14.6 inches high, 6 inches in diameter) on a frequency of 1300 MHz. Using the same reception is an estimate of the gain of the antenna at 2db we have a power of 56db so 375 W at the nearest orbital point.

5) Is the gain estimate of the antenna good?
6) Is the power realistic?

Moreover the top for a mission "low cost" would not have passed through the deep space network but receive the messages by radio amateurs so:

7) What is the minimum power of reception of an amateur radio system?
8) What is the maximum gain of an amateur radio antenna?

Thank you for your attention.